Climate Glossary from OneEarth.org

Climate Glossary


Climate Glossary of Terms and Definitions

Climate Glossary. Review this content to help understand what is going on with the climate crisis and what we can do about it.

Climate change refers to significant changes in global temperature, precipitation, wind patterns and other measures of climate that occur over several decades or longer.

Study this climate glossary to understand climate change better.

The seas are rising. The foods we eat and take for granted are threatened. Ocean acidification is increasing. Ecosystems are changing, and for some, that could spell the end of certain regions the way we have known them. And while some species are adapting, for others, it’s not that easy.

Evidence suggests many of these extreme climate changes are connected to rising levels of carbon dioxide and other greenhouse gases in the Earth’s atmosphere — more often than not, the result of human activities.

Search below for key terms and definitions related to climate change.

Aerosols are small suspended particles in a gas. Scientists can detect them in the atmosphere. They range in size from one nanometer (one billionth of a meter) to 100 micrometers (one millionth of a meter).

Antarctic sea ice

Antarctic sea ice is nearly a geographic opposite of its Arctic counterpart because Antarctica is a landmass covered in ice surrounded by an ocean, and the Arctic is an ocean of sea ice surrounded by land.

Anthropogenic describes a process or result generated by human beings.

Aquaculture

Aquaculture uses a body of water for the cultivation of plants and animals. (Compare to agriculture, which uses land to cultivate plants and animals.) Ponds, lakes, rivers, and the ocean serve as places to breed, rear and harvest aquatic species.

Aquifer is water-bearing rock from which water can be pumped.

Arctic sea ice

Arctic sea ice is an integral part of the Arctic Ocean and an important indicator of climate change. During winter’s dark months, sea ice will typically cover the majority of the Arctic Ocean.

Biofuels are renewable fuels derived from biological materials, such as algae and plants, that can be regenerated. This distinguishes them from fossil fuels, which are considered nonrenewable. Example of biofuels are ethanol, methanol and biodiesel.

Biogenic emissions are emissions generated by living things.

Biological productivity is a measure of the amount of plant and animal growth in a defined region and time.

Carbon is a configuration of molecules and an elemental building block of all organisms on Earth.

Carbon cycle describes the process by which living things absorb carbon from the atmosphere, sediments and soil, or food. To complete the cycle, carbon returns to the atmosphere in the form of carbon dioxide or methane by respiration, combustion or decay.

Carbon dioxide is the gas that accounts for about 84 percent of total U.S. greenhouse gas emissions. In the U.S. the largest source of carbon dioxide (98 percent) emissions is combustion of fossil fuels. Combustion can be from mobile (vehicles) or stationary sources (power plants). As energy use increases, so do carbon dioxide emissions.

Carbon sequestration

Carbon sequestration is the process of removing carbon from the atmosphere and storing it in a fixed molecule in soil, oceans or plants. An organism or landscape that stores carbon is called a carbon sink. An organism or landscape that emits carbon is called a carbon source. For example, soils contain inorganic carbon (calcium carbonate) and organic carbon (humus) and can be either a source or a sink for atmospheric carbon dioxide, depending on how landscapes are managed. Because large amounts of carbon are stored in soils, small changes to soil can have major impacts on atmospheric carbon dioxide.

Climate change adaptation

Climate change adaptation refers to the adjustments societies or ecosystems make to limit the negative effects of climate change or to take advantage of opportunities provided by a changing climate. Adaptation can range from farmers planting more drought-resistant crops to coastal communities evaluating how best to protect themselves from sea level.

Climate forcing refers to how climate affects the physical, chemical and biological attributes of a region.

Climate science

Climate science studies how changing climates affect the natural order on a global level. Rising global temperatures bring with them the potential to raise sea levels to raise sea levels, change precipitation and local climate conditions.

Coastal Wetlands

Coastal wetlands include saltwater and freshwater wetlands located within coastal watersheds — specifically USGS 8-digit hydrologic unit watersheds which drain into the Atlantic Ocean, Pacific Ocean, or Gulf of Mexico.

Dimethylsulfide is the most abundant biological sulfur compound emitted to the atmosphere, mostly from phytoplankton, and encourages cloud formation.

Ecosystem services are the benefits or “services” of an ecosystem to human life, such as clean water and the decomposition of organic matter.

Electrolytes are chemical substances containing free ions that conduct electricity.

Emissions are substances released into the air and are measured by their concentrations, or parts per million, in the atmosphere.

Feedstock is raw material, usually plant or agricultural waste, that can be processed into fuel or energy.

Glaciers

Glaciers and ice caps form on land. Glaciers accumulate snow, which over time becomes compressed into ice. On average, glaciers worldwide have been losing mass since at least the 1970s.

Global temperature is an average of air temperature recordings from weather stations on land and sea as well as some satellite measurements. Worldwide, 2006-2015 was the warmest decade on record since thermometer-based observations began nearly 150 years ago.

In the early 1960s scientists recognized that carbon dioxide in the atmosphere was increasing. Later they discovered that methane, nitrous oxide and other gases were rising. Because these gases trap heat and warm the Earth, as a greenhouse traps heat from the sun, scientists concluded that increasing levels of “greenhouse gases” would increase global warming.

Global Warming Potential (GWP) is the ability of a greenhouse gas to absorb heat compared to carbon dioxide over a specified period of time, from 20 to 500 years. The timeframe is important because each gas has a different rate at which it is removed from the atmosphere. For each time period, carbon dioxide is always set at “1”, and other greenhouse gases are compared to carbon dioxide for the same timeframe. For example, the sulfur hexafluoride’s GWP at 20 years is 15,100, meaning it has 15,100 times more warming potential than carbon dioxide in that timeframe.

The main greenhouse gases are water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). Water vapor is the most plentiful at about one percent. The next most plentiful is carbon dioxide at 0.04 percent. The effect of human activity on global water vapor concentrations is too small to be important. The effects of human activity on the other greenhouse gases, however, is large and very important. These gases are increasing faster than they are removed from the atmosphere.

Heat domes

A heat dome is when hot ocean air gets trapped over a large area, resulting in dangerously high temperatures. It occurs when high atmospheric pressure forms over a region, pushing air down, which heats as the air compresses. This forms a “lid” that seals to create a dome of trapped heat, setting the stage for heat waves.

Hydrologic cycle is the process by which water moves around the earth. The cycle includes evaporation, precipitation, runoff, condensation, transpiration and infiltration.

Hydrologic model is a computer analysis of large amounts of historical data. It helps predict how variables such as temperature, rain, and carbon dioxide levels might affect the hydrologic cycle.

Ice Loss

Ice loss refers to the retreat of sea ice and land ice mass from its historic extents. This retreat of sea ice and land ice is one of two major causes of the current sea level rise.

An ice sheet forms on land and extends over tens of thousands of miles. Greenland and Antarctica have vast ice sheets that together contain more than 99 percent of the freshwater ice on Earth. In Greenland, today’s record summer melts bring rapid and widespread ice sheet loss. In Antarctica, the melt is slower and more localized for now.

Ice Shelf

An ice shelf forms from the outflow of land ice and floats on the sea at the land’s edge. It creates a barrier that slows the flow of land ice into the ocean. In the last thirty years, both rapid disintegration of ice shelves and ice shelf collapses have been observed along Canada and the Antarctic Peninsula.

Methane is a gas and represents about 8 percent of total U.S. greenhouse gas emissions. The largest sources are wood burning in stoves and fireplaces, livestock digestive systems, and decomposition in landfills.

Mesoscale is a measure of distance useful for local winds, thunderstorms and tornadoes. It ranges from a few to a few hundred miles.

A micron, also called a micrometer, is one millionth of a meter, or a thousandth of a millimeter. It is a common measure for particulate matter in the atmosphere. Particles measuring only 2.5 microns (approximately 1/30th the average width of a human hair) lodge deeply into the lungs.

Mitigation potential is a measurement of the amount of carbon that can be stored in order to balance the release of carbon. It is important in discussions about power plants and vehicles.

Nano refers to nanometer, one billionth of a meter or a hundred-thousandth of a millimeter.

Nitrous oxide is one of six gases addressed by the Kyoto Protocol international agreement and the main regulator of stratospheric ozone. Animal waste and nitrogen fertilization of soil are the largest contributors. Nitrogen emissions have nearly 300 times the global warming potential of carbon dioxide over 100 years.

Ocean acidification

Ocean acidification is the change in ocean chemistry due to decreasing pH levels, or increasing acidity, in seawater.

Ground level ozone is a gas produced through reactions between nitrous oxides (NOX) and volatile organic compounds (VOCs) when burning coal, gasoline and other fuels. VOCs are found in solvents, paints, hairsprays and more common items. Ozone consists of three oxygen atoms and is the main component of smog.

Stratospheric ozone is a gas found in a layer from six to 25 miles above the Earth’s surface. It acts as a barrier to global warming. Specifically, the ozone layer keeps 95-99% of the sun’s ultraviolet radiation from striking the Earth.

Ozone forming potential is a measure of the reactivity of an individual chemical compound to the presence of other chemicals that form ozone together.

Particulate matter (PM-10) are aerosols including dust, soot and tiny bits of solid materials that are released and move around in the air. Sources are burning of diesel fuels, incineration of garbage, mixing and applying fertilizers and pesticides, road construction, steel making, mining, field burning, forest fires, fireplaces and woodstoves. PM causes eye, nose and throat irritation and respiratory problems.

Polar Vortex

The polar vortex is a large area of low pressure and cold air around Earth’s North Pole. The phenomenom typically goes unnoticed by those of us living in lower latitudes except for when, every once in a while, the air pressure and winds shift.

Primary production is the production of organic compounds from atmospheric or aquatic carbon dioxide, principally through the process of photosynthesis.

Renewable energy is energy from sources that will renew themselves within our lifetime. Renewable energy sources include wind, sun, water, biomass (vegetation) and geothermal heat.

Sea ice, both Antarctic and Arctic seas, forms from salty ocean water. Overall, the Earth has lost a mass of sea ice the size of Maryland each year since 1979.

Sea level is the average level between high tide and low tide where the surface of the sea meets a shoreline.

Sea level rise

Sea level rise describes an increase in the average level between high tide and low tide where the surface of the sea meets a shoreline.

Seed particles are tiny solid or liquid particles that provide a non-gaseous surface. The surface allows water to make the transition from a vapor to a liquid.

Sediment data are materials and measurements obtained from taking a vertical core of lake bottom sediment and analyzing the layers.

Sensitivity analysis is an interpretation of different sources of variation in the output of a predictive model.

The solar cycle describes the sun’s activity over its eleven-year period of movement and related variations. The cycle was first determined in 1843 by German astronomer Heinrich Schwabe. Scientists are trying to determine how much solar variations affect the temperature of Earth’s atmosphere.

Solar Power

Solar power refers to the energy harnessed from the sun, which can then be transformed into different types of energy, including thermal and electric.

Stratosphere is a layer of the atmosphere nine to 31 miles above the Earth. Ozone in the stratosphere filters out harmful sun rays, including a type of sunlight called ultraviolet B. This type of light causes health and environmental damage.

Synoptic is used to describe a large-scale weather system more than 200 miles across.

Thermochemical technologies are methods of capturing the energy potential of biomass.

Thermodynamic modules are the portions of models that predict changes in aerosols due to temperature.

Tillage refers to cultivation of the soil to improve production of crops.

Trace gases make up only one percent of the atmosphere. Most of the atmosphere is made up of nitrogen (78 percent by volume) and oxygen (21 percent by volume).

Transpiration is the evaporation of water into the atmosphere from the leaves and stems of plants. It accounts for approximately 90 percent of all evaporating water.

Transportation Control Measures describe travel demand management measures to help reduce air pollutants from transportation sources.

Volatile organic compounds, or volatile organic carbon, are chemical compounds from solids or liquids that are emitted as gases. VOCs are emitted by thousands of man-made sources including paints, lacquers, cleaning supplies, pesticides, building materials, furnishings, copiers, correction fluids, adhesives, permanent markers, cleaners and disinfectants, fuels, crude oil and cosmetics. Natural sources are trees, termites, cows (ruminants) and agricultural cultivation.

Water column is the full depth of a lake from the surface to the bottom.

Wildfire

Wildfires are unplanned burns in any natural environment, like a forest or a grassland. Wildfire can spread quickly, burning through most anything in their path, causing injury and death to people and animals.

More terminology and definitions

Here is a list of 200 terms related to climate change, along with brief definitions for each:

1. **Adaptation** - Adjustments in systems or behaviors to reduce vulnerability to climate change impacts.
2. **Albedo** - The reflectivity of a surface, with higher albedo surfaces reflecting more solar energy.
3. **Anthropogenic** - Resulting from the influence of human beings on nature.
4. **Atmosphere** - The envelope of gases surrounding the Earth or another planet.
5. **Biofuel** - Fuel derived directly from living matter, such as plants.
6. **Biodiversity** - The variety of life in the world or in a particular habitat or ecosystem.
7. **Biome** - A large naturally occurring community of flora and fauna occupying a major habitat.
8. **Biosphere** - The global sum of all ecosystems, including all life forms and their relationships.
9. **Carbon Capture and Storage (CCS)** - Technologies that capture CO2 emissions, transporting and storing them underground to prevent release into the atmosphere.
10. **Carbon Cycle** - The process by which carbon is exchanged between the Earth's various carbon sinks and sources.
11. **Carbon Dioxide (CO2)** - A colorless gas produced by burning carbon and organic compounds and by respiration.
12. **Carbon Footprint** - The total amount of greenhouse gases emitted directly or indirectly by an individual, organization, event, or product.
13. **Carbon Neutral** - Achieving net zero carbon dioxide emissions by balancing emissions with carbon removal or offsetting.
14. **Carbon Offset** - A reduction in emissions of carbon dioxide or other greenhouse gases made to compensate for emissions made elsewhere.
15. **Carbon Sequestration** - The process of capturing and storing atmospheric carbon dioxide.
16. **Carbon Sink** - A natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period.
17. **Carbon Tax** - A tax levied on the carbon content of fuels to mitigate emissions of carbon dioxide.
18. **Chlorofluorocarbons (CFCs)** - Chemical compounds used in aerosols, refrigerants, foam blowing agents, and solvents that are harmful to the ozone layer.
19. **Climate** - The weather conditions prevailing in an area over a long period.
20. **Climate Change** - A long-term change in the average weather patterns that have come to define Earth’s local, regional, and global climates.
21. **Climate Model** - A mathematical representation of the interrelated systems that determine the Earth’s climate processes.
22. **CO2 Equivalent** - A metric measure used to compare the emissions from various greenhouse gases on the basis of their global warming potential.
23. **Deforestation** - The permanent destruction of forests in order to make the land available for other uses.
24. **Desertification** - The process by which fertile land becomes desert, typically as a result of drought, deforestation, or inappropriate agriculture.
25. **Ecosystem** - A biological community of interacting organisms and their physical environment.
26. **El Niño** - A climate pattern that describes the unusual warming of surface waters in the eastern tropical Pacific Ocean.
27. **Emissions** - The act of releasing something, especially gas or radiation, into the environment.
28. **Fossil Fuels** - Natural fuels such as coal, oil, and natural gas, formed from the remains of living organisms.
29. **Geoengineering** - Deliberate large-scale interventions in the Earth’s natural systems to counteract climate change.
30. **Glacier** - A slowly moving mass of ice formed by the accumulation and compaction of snow.
31. **Global Warming** - An increase in Earth's average surface temperature due to rising levels of greenhouse gases.
32. **Greenhouse Effect** - The trapping of the sun's warmth in a planet's lower atmosphere due to greater transparency of the atmosphere to visible radiation from the sun than to infrared radiation emitted from the planet's surface.
33. **Greenhouse Gases (GHGs)** - Gases that trap heat in the atmosphere, such as carbon dioxide, methane, and nitrous oxide.
34. **Habitat** - The natural home or environment of an animal, plant, or other organism.
35. **Hydrofluorocarbons (HFCs)** - Compounds containing hydrogen, fluorine, and carbons, used as refrigerants, blowing agents, and solvents and considered potent greenhouse gases.
36. **Ice Cap** - A covering of ice over a large area, especially on the polar region of a planet.
37. **IPCC (Intergovernmental Panel on Climate Change)** - A United Nations body assessing the science related to climate change.
38. **Kyoto Protocol** - An international treaty that commits state parties to reduce greenhouse gas emissions, based on the premise that global warming exists and is being caused by human activity.
39. **Land Use** - The management and modification of natural environment or wilderness into built environment.
40. **Methane (CH4)** - A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 28–36 times that of CO2.
41. **Mitigation** - The action of reducing the severity, seriousness, or painfulness of something, especially climate change.
42. **Montreal Protocol** - An international treaty designed to protect the ozone layer by phasing out the production of a number of substances believed to be responsible for ozone depletion.
43. **Ocean Acidification** - The ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide (CO2) from the atmosphere.
44. **Ozone (O3)** - A colorless unstable toxic gas with a pungent odor and powerful oxidizing properties, formed from oxygen by electrical discharges or ultraviolet light.
45. **Ozone Layer** - A layer in the earth's stratosphere containing a high concentration of ozone, which absorbs most of the ultraviolet radiation reaching the earth from the sun.
46. **Paris Agreement** - An agreement within the United Nations Framework Convention on Climate Change dealing with greenhouse gas emissions mitigation, adaptation, and finance starting in the year 2020.
47. **Particulates** - Tiny particles of solid or liquid suspended in a gas or liquid.
48. **Permafrost** - Ground, including rock or (cryotic) soil, at or below the freezing point of water for two or more years.
49. **Photosynthesis** - The process by which green plants and some other organisms use sunlight to synthesize foods from carbon dioxide and water.
50. **Renewable Energy** - Energy from a source that is not depleted when used, such as wind or solar power.
51. **Resilience** - The capacity to recover quickly from difficulties; toughness, especially in the context of ecosystems and environments.
52. **Sea Level Rise** - An increase in the level of the world’s oceans due to the effects of global warming.
53. **Solar Radiation** - Radiation from the sun.
54. **Sustainability** - Avoidance of the depletion of natural resources in order to maintain an ecological balance.
55. **Sustainable Development** - Economic development that is conducted without depletion of natural resources.
56. **Thermal Expansion** - The tendency of matter to change in shape, area, and volume in response to a change in temperature.
57. **Tipping Point** - The point at which a series of small changes or incidents becomes significant enough to cause a larger, more important change.
58. **UNFCCC (United Nations Framework Convention on Climate Change)** - An international environmental treaty aimed at preventing "dangerous" human interference with the climate system.
59. **Weather** - The state of the atmosphere at a place and time as regards heat, dryness, sunshine, wind, rain, etc.
60. **Wildfire** - A large, destructive fire that spreads quickly over woodland or brush.
61. **Xeriscaping** - A style of landscape design requiring little or no irrigation or other maintenance, used in arid regions.
62. **Zero Emissions** - An engine, motor, process, or other energy source that does not produce any gas or other pollutant.

63. **Carbon Trading** - A market-based system aimed at reducing greenhouse gases that allows countries or entities to buy or sell units of greenhouse gas emissions to meet their national limits.

64. **Climatology** - The scientific study of climate, scientifically defined as weather conditions averaged over a period of time.

65. **COP (Conference of the Parties)** - The supreme decision-making body of the United Nations Framework Convention on Climate Change, where member states meet to review and assess progress.

66. **Decarbonization** - The process of reducing or eliminating carbon dioxide emission from energy sources.

67. **Ecological Footprint** - The impact of a person or community on the environment, expressed as the amount of land required to sustain their use of natural resources.

68. **Ecosystem Services** - The benefits that humans freely gain from the natural environment and from properly-functioning ecosystems.

69. **Energy Efficiency** - Using less energy to provide the same service or achieving more with the same amount of energy.

70. **Feed-in Tariff** - A policy mechanism designed to accelerate the investment in renewable energy technologies by providing them remuneration above the retail or wholesale rates of electricity.

71. **Floodplain** - An area of land adjacent to a river which stretches from the banks of the river to the outer edges of the valley.

72. **Geothermal Energy** - Heat energy generated and stored in the Earth, which can be harnessed to generate electricity or for heating and cooling.

73. **Green Economy** - An economy that aims at reducing environmental risks and ecological scarcities, and that aims for sustainable development without degrading the environment.

74. **Hydrology** - The branch of science concerned with the properties of the earth's water, especially its movement in relation to land.

75. **Impact Assessment** - The process of identifying the future consequences of a current or proposed action related to the environment.

76. **Invasive Species** - plants, fungi, or animals that are not native to a specific location and have a tendency to spread, which is believed to cause damage to the environment, human economy, or human health.

77. **Land Degradation** - The process by which the quality of the land is reduced through human activities or natural disasters.

78. **Microclimate** - The climate of a small, specific place within a larger area as contrasted with the climate of the entire area.

79. **Natural Capital** - The world’s stocks of natural assets which include geology, soil, air, water and all living things.

80. **Non-Renewable Energy** - Energy from sources that cannot be replenished in a short amount of time, such as fossil fuels like coal and oil.

81. **Oceanography** - The branch of Earth science that studies the ocean, including marine organisms and ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor; and fluxes of various chemical substances and physical properties within the ocean and across its boundaries.

82. **Peatland** - Type of wetland that accumulates plant material, including mosses, in a water-saturated environment, often used as a carbon sink.

83. **Phenology** - The study of cyclic and seasonal natural phenomena, especially in relation to climate and plant and animal life.

84. **Pollution** - The introduction of contaminants into the natural environment that cause adverse change.

85. **Radiative Forcing** - The difference between sunlight absorbed by the Earth and energy radiated back to space, used to assess and compare the strength of the different climate change mechanisms.

86. **Reforestation** - Replanting of forests on lands that have previously contained forests but that have been converted to some other use.

87. **Reservoir** - A large natural or artificial lake used as a source of water supply.

88. **Smog** - Fog or haze combined with smoke and other atmospheric pollutants.

89. **Soil Erosion** - The wearing away of topsoil, which is the top layer of soil and is the most fertile because it contains the most organic, nutrient-rich materials.

90. **Solar Power** - Power obtained by harnessing the energy of the sun's rays.

91. **Species Extinction** - The end of an organism or of a group of organisms (taxon), normally a species.

92. **Stewardship** - The job of supervising or taking care of something, such as an organization or property, especially in terms of environmental conservation.

93. **Sustainable Agriculture** - Farming in sustainable ways based on an understanding of ecosystem services, the study of relationships between organisms and their environment.

94. **Tidal Energy** - A form of hydropower that converts the energy of tides into useful forms of power, mainly electricity.

95. **Urban Heat Island** - A metropolitan area that's a lot warmer than the rural areas surrounding it due to human activities.

96. **Vector-Borne Disease** - Infectious diseases that are transmitted by vectors such as mosquitoes, ticks, or fleas.

97. **Water Cycle** - The cycle of processes by which water circulates between the earth's oceans, atmosphere, and land, involving precipitation as rain and snow, drainage in streams and rivers, and return to the atmosphere by evaporation and transpiration.

98. **Water Scarcity** - The lack of sufficient available fresh water resources to meet the demands of water usage within a region.

99. **Weatherization** - The practice of protecting a building and its interior from the elements, particularly from sunlight, precipitation, and wind, and of modifying a building to reduce energy consumption and optimize energy efficiency.

100. **Wetland** - Land consisting of marshes or swamps; saturated land.

101. **Wildlife Corridor** - Strips of natural habitat that connect populations of wildlife that have been separated by human activities like roads or development.

102. **Zero-Carbon** - Producing or emitting no carbon emissions from fossil fuels.
103. **Biochar** - Charcoal that is produced by pyrolysis of biomass and is used especially as a soil amendment and in carbon sequestration.
104. **Biomass** - The total mass of organisms in a given area or volume; organic matter used as a fuel, especially in a power station for the generation of electricity.
105. **Cap and Trade** - A market-based approach to controlling pollution by providing economic incentives for achieving reductions in the emissions of pollutants.
106. **Climate Analytics** - The use of data and statistical analysis to model and predict climate patterns and trends.
107. **Climate Finance** - Financing aimed at reducing emissions, and enhancing sinks of greenhouse gases through various projects and programs.
108. **Climate Negotiation** - The diplomatic discussions aimed at achieving agreements between countries on climate change issues.
109. **Cryosphere** - The frozen water part of the Earth system, including glaciers, snow, ice caps, and icebergs.
110. **Ecological Migration** - The planned relocation of populations away from vulnerable environments.
111. **Ecosystem Collapse** - A situation where an ecosystem suffers a sharp reduction in its ability to provide ecosystem services.
112. **Energy Storage** - The capture of energy produced at one time for use at a later time, a key technology in the transition to a clean energy system.
113. **Environmental Audit** - A type of evaluation intended to identify environmental compliance and management system implementation gaps, along with related corrective actions.
114. **Environmental Degradation** - The deterioration of the environment through depletion of resources such as air, water, and soil; the destruction of ecosystems, and the extinction of wildlife.
115. **Flood Risk Assessment** - The process used to determine the risk associated with floods in a particular region by analyzing potential losses.
116. **Fuel Cell** - A device that generates electricity by a chemical reaction via conversion of fuel (hydrogen) into electricity.
117. **GIS (Geographical Information System)** - A system designed to capture, store, manipulate, analyze, manage, and present spatial or geographic data.
118. **Glacial Retreat** - The process by which glaciers melt and reduce in size and extent.
119. **Global Dimming** - A decrease in the amounts of solar radiation reaching the surface of the Earth, attributed to aerosols and other pollutants.
120. **Green Building** - Building projects that would normally use sustainable materials and incorporate energy-efficient and water-saving technologies.
121. **Greenwashing** - Disinformation disseminated by an organization so as to present an environmentally responsible public image.
122. **Hazardous Waste** - Waste that has substantial or potential threats to public health or the environment.
123. **Habitat Fragmentation** - The process by which habitats are altered or divided by external factors, typically human activities like logging and urbanization.
124. **Heat Wave** - A prolonged period of excessively hot weather, which may be accompanied by high humidity.
125. **Hybrid Vehicles** - Vehicles that use two or more distinct types of power, such as an internal combustion engine and an electric motor.
126. **Indigenous Knowledge** - The unique, traditional, local knowledge existing within and developed around the specific conditions of people indigenous to a particular geographic area.
127. **Infrared Radiation** - Radiation that has a wavelength longer than visible light but shorter than microwaves.
128. **Integrated Pest Management (IPM)** - An ecological approach to pest management that combines biological, cultural, physical, and chemical tools in a way that minimizes economic, health, and environmental risks.
129. **Jet Stream** - Fast flowing, narrow air currents found in the atmosphere around 10 kilometers above the surface of the Earth.
130. **Landfill Gas** - A complex mix of different gases created by the action of microorganisms within a landfill.
131. **Life Cycle Assessment** - The assessment of the environmental impacts associated with all the stages of the life of a commercial product, process, or service.
132. **Low-Impact Development** - An approach to land development (or re-development) that works with nature to manage stormwater as close to its source as possible.
133. **Mangroves** - Tropical trees that grow in conditions of high salinity, either along sea coasts or on the edges of brackish water bodies like estuaries.
134. **Marine Protected Area** - Regions in oceans where human activity has been placed under some restrictions for conservation and protection purposes, often to preserve biological diversity.
135. **Microplastics** - Extremely small pieces of plastic debris in the environment resulting from the disposal and breakdown of consumer products and industrial waste.
136. **Natural Disaster** - A major adverse event resulting from natural processes of the Earth, examples include floods, hurricanes, tornadoes, volcanic eruptions, and tsunamis.
137. **Nitrous Oxide (N2O)** - A greenhouse gas with significant global warming potential, largely produced by soil cultivation practices, especially the use of commercial and organic fertilizers.
138. **Ocean Gyres** - Large systems of circulating ocean currents, particularly those involved with large wind movements.
139. **Particulate Matter (PM)** - A mixture of solid particles and liquid droplets found in the air, some of which can be inhalable and pose serious health risks.
140. **Passive Solar** - The use of sunlight for useful energy without use of active mechanical systems (as contrasted to active solar).
141. **Peak Oil** - The theorized point in time when the maximum rate of extraction of petroleum is reached, after which it is expected to enter terminal decline.
142. **Photosynthetic Efficiency** - The fraction of light energy converted into chemical energy during photosynthesis in plants and algae.
143. **Polar Vortex** - A large area of low pressure and cold air surrounding both of the Earth’s poles, strengthening in the winter and weakening in the summer.
144. **Pollinator Decline** - A reduction in the number of pollinators in many ecosystems worldwide, which is troubling because many plant species rely on pollinators for reproduction.
145. **Precipitation** - Any form of water - liquid or solid - falling from the sky, including rain, snow, sleet, and hail.
146. **Prescribed Burn** - The process of planning and applying fire to a predetermined area, under specific environmental conditions, to achieve a desired outcome.
147. **Psychrometry** - The field of engineering concerned with the physical and thermodynamic properties of gas-vapor mixtures.
148. **Pumped-Storage Hydroelectricity** - A type of hydroelectric power generation used for load balancing where water is pumped from a lower elevation reservoir to a higher elevation.
149. **Radiation Budget** - The balance between incoming and outgoing solar and terrestrial radiation, influenced by atmospheric conditions including clouds and greenhouse gases.
150. **Radioactive Waste** - Waste that contains radioactive material, usually a by-product of nuclear power generation and other applications of nuclear fission or nuclear technology.
151. **Range Shift** - The movement of species, including plants and animals, to higher elevations or latitudes in response to changing environmental conditions.
152. **Recycling** - The process of converting waste materials into new materials and objects, a key component of modern waste reduction.
153. **Renewable Portfolio Standard** - A regulation that requires the increased production of energy from renewable energy sources, such as wind, solar, biomass, and geothermal.
154. **Reservoir Emissions** - Greenhouse gas emissions from artificial lakes or reservoirs from substances like decomposed vegetation.
155. **Resource Management** - The efficient and effective deployment of an organization's resources when they are needed.
156. **Retrofitting** - Adding new technology or features to older systems, like installing new windows or insulation to older buildings to improve energy efficiency.
157. **Riparian Rights** - The rights of landowners whose land abuts a river or stream to make reasonable use of it.
158. **Risk Assessment** - A systematic process of evaluating the potential risks that may be involved in a projected activity or undertaking.
159. **Runoff** - The draining away of water (or substances carried in it) from the surface of an area of land, a building or structure.
160. **Salinity** - The saltiness or amount of salt dissolved in a body of water, called saline water.
161. **Seagrass** - Flowering plants which grow in marine environments from the tropics to the Arctic Circle.
162. **Sedimentation** - The process of settling or being deposited as a sediment.
163. **Silviculture** - The practice of controlling the growth, composition, health, and quality of forests to meet diverse needs and values.
164. **Sinkhole** - A cavity in the ground, especially in limestone bedrock, caused by water erosion and providing a route for surface water to disappear underground.
165. **Smog Alerts** - Notifications issued by government agencies or health organizations when levels of air pollution are high and posing health risks.
166. **Snowpack** - A seasonal accumulation of slow-melting snow.
167. **Soil Carbon Storage** - The process by which CO2 is removed from the atmosphere and stored in the soil carbon pool.
168. **Solar Farm** - A large-scale solar photovoltaic system designed for the supply of merchant power into the electricity grid.
169. **Species Diversity** - The number of different species that are represented in a given community (a dataset).
170. **Storm Surge** - An offshore rise of water associated with a low pressure weather system, primarily tropical cyclones.
171. **Stratosphere** - The second major layer of Earth’s atmosphere, just above the troposphere, and below the mesosphere.
172. **Subsidence** - The gradual caving in or sinking of an area of land.
173. **Sustainable Fisheries** - A fishery that is harvested at a sustainable rate, where the fish population does not decline over time because of fishing practices.
174. **Tailings** - The materials left over after the process of separating the valuable fraction from the uneconomic fraction (gangue) of an ore.
175. **Temperate Zone** - The regions of the Earth between the tropics and the polar circles, having a climate that is warm in the summer, cold in the winter, and moderate in the spring and fall.
176. **Terraforming** - The hypothetical process of deliberately modifying the atmosphere, temperature, surface topography, or ecology of a planet, moon, or other body to be similar to the environment of Earth.
177. **Thermal Pollution** - A temperature increase in natural water bodies caused by human influence, such as the use of water as coolant in a power plant.
178. **Topography** - The arrangement of the natural and artificial physical features of an area.
179. **Toxic Release Inventory (TRI)** - A publicly available database containing information on toxic chemical emissions from certain industries and federal facilities, mandated by the U.S. EPA.
180. **Transboundary Pollution** - Pollution that originates in one country but can cause damage in another country’s environment, by crossing borders through pathways like water or air.
181. **Tree Line** - The edge of the habitat at which trees are capable of growing.
182. **Trophic Level** - Each of several hierarchical levels in an ecosystem, comprising organisms that share the same function in the food chain and the same nutritional relationship to the primary sources of energy.
183. **Tsunami** - A long high sea wave caused by an earthquake, submarine landslide, or other disturbance.
184. **Turbidity** - The cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air.
185. **Urban Planning** - A technical and political process concerned with the development and design of land use and the built environment.
186. **Vapor Recovery** - The process of collecting the vapors of gasoline and other fuels, so that they do not escape into the atmosphere.
187. **Vector Control** - Methods to limit or eradicate the mammals, birds, insects or other arthropods which transmit disease pathogens.
188. **Ventilation** - The supply of air to a space that ensu...
189. **Volcanic Ash** - Small fragments of rock and volcanic glass created during volcanic eruptions.
190. **Waste Minimization** - Processes and policies that reduce the amount of waste produced by a person or a society.
191. **Water Conservation** - The careful management and use of water resources to ensure their sustainability and availability in the future.
192. **Water Quality** - The chemical, physical, biological, and radiological characteristics of water, especially those which affect its suitability for a particular purpose.
193. **Water Table** - The level below which the ground is completely saturated with water.
194. **Weather Forecasting** - The application of science and technology to predict the state of the atmosphere for a future time at a specific location.
195. **Wetlands Restoration** - The practice of renewing and restoring wetland ecosystems that have been degraded, damaged, or destroyed.
196. **Wind Farm** - A group of wind turbines in the same location used to produce electricity.
197. **Xerophyte** - A plant adapted to an arid environment with mechanisms to store and conserve water.
198. **Zooplankton** - Small and often microscopic animals that inhabit watery environments, both salty and fresh.
199. **Zoning** - Legislative process for dividing land into zones for different uses.
200. **Climatic Zones** - Areas of the Earth that are divided according to prevalent climate patterns.

This completes the list of 200 terms commonly used in discussions about climate change, each with a succinct definition to enhance understanding of the topic.

More climate terminology and definitions

Abrupt Climate Change
Sudden (on the order of decades), large changes in some major component of the climate system, with rapid, widespread effects.

Adaptation
Adjustment or preparation of natural or human systems to a new or changing environment which moderates harm or exploits beneficial opportunities.

Adaptive Capacity
The ability of a system to adjust to climate change (including climate variability and extremes) to moderate potential damages, to take advantage of opportunities, or to cope with the consequences.

Aerosols
Small particles or liquid droplets in the atmosphere that can absorb or reflect sunlight depending on their composition.

Afforestation
Planting of new forests on lands that historically have not contained forests. [1]

Albedo
The amount of solar radiation reflected from an object or surface, often expressed as a percentage.

Alternative Energy
Energy derived from nontraditional sources (e.g., compressed natural gas, solar, hydroelectric, wind). [2]

Annex I Countries/Parties
Group of countries included in Annex I (as amended in 1998) to the United Nations Framework Convention on Climate Change, including all the developed countries in the Organization of Economic Co-operation and Development, and economies in transition. By default, the other countries are referred to as Non-Annex I countries. Under Articles 4.2 (a) and 4.2 (b) of the Convention, Annex I countries commit themselves specifically to the aim of returning individually or jointly to their 1990 levels of greenhouse gas emissions by the year 2000. [2]

Anthropogenic
Made by people or resulting from human activities. Usually used in the context of emissions that are produced as a result of human activities. [3]

Atmosphere
The gaseous envelope surrounding the Earth. The dry atmosphere consists almost entirely of nitrogen (78.1% volume mixing ratio) and oxygen (20.9% volume mixing ratio), together with a number of trace gases, such as argon (0.93% volume mixing ratio), helium, radiatively active greenhouse gases such as carbon dioxide (0.035% volume mixing ratio), and ozone. In addition the atmosphere contains water vapor, whose amount is highly variable but typically 1% volume mixing ratio. The atmosphere also contains clouds and aerosols. [1]

Atmospheric Lifetime
Atmospheric lifetime is the average time that a molecule resides in the atmosphere before it is removed by chemical reaction or deposition. In general, if a quantity of a compound is emitted into the atmosphere at a particular time, about 35 percent of that quantity will remain in the atmosphere at the end of the compound's atmospheric lifetime. This fraction will continue to decrease in an exponential way, so that about 15 percent of the quantity will remain at the end of two times the atmospheric lifetime, etc. (Some compounds, most notably carbon dioxide, have more complex lifecycles, and their atmospheric lifetimes are not defined by a simple exponential equation.) Greenhouse gas lifetimes can range from a few years to a few thousand years.

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B

Biofuels
Gas or liquid fuel made from plant material. Includes wood, wood waste, wood liquors, peat, railroad ties, wood sludge, spent sulfite liquors, agricultural waste, straw, tires, fish oils, tall oil, sludge waste, waste alcohol, municipal solid waste, landfill gases, other waste, and ethanol blended into motor gasoline. [4]

Biogeochemical Cycle
Movements through the Earth system of key chemical constituents essential to life, such as carbon, nitrogen, oxygen, and phosphorus. [3]

Biomass
Materials that are biological in origin, including organic material (both living and dead) from above and below ground, for example, trees, crops, grasses, tree litter, roots, and animals and animal waste. [4]

Biosphere
The part of the Earth system comprising all ecosystems and living organisms, in the atmosphere, on land (terrestrial biosphere) or in the oceans (marine biosphere), including derived dead organic matter, such as litter, soil organic matter and oceanic detritus. [1]

Black Carbon Aerosol
Black carbon (BC) is the most strongly light-absorbing component of particulate matter (PM), and is formed by the incomplete combustion of fossil fuels, biofuels, and biomass. It is emitted directly into the atmosphere in the form of fine particles (PM2.5).

Borehole
Any exploratory hole drilled into the Earth or ice to gather geophysical data. Climate researchers often take ice core samples, a type of borehole, to predict atmospheric composition in earlier years. See ice core.

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C

Carbon Cycle
All parts (reservoirs) and fluxes of carbon. The cycle is usually thought of as four main reservoirs of carbon interconnected by pathways of exchange. The reservoirs are the atmosphere, terrestrial biosphere (usually includes freshwater systems), oceans, and sediments (includes fossil fuels). The annual movements of carbon, the carbon exchanges between reservoirs, occur because of various chemical, physical, geological, and biological processes. The ocean contains the largest pool of carbon near the surface of the Earth, but most of that pool is not involved with rapid exchange with the atmosphere. [3]

Carbon Dioxide
A naturally occurring gas, and also a by-product of burning fossil fuels and biomass, as well as land-use changes and other industrial processes. It is the principal human caused greenhouse gas that affects the Earth's radiative balance. It is the reference gas against which other greenhouse gases are measured and therefore has a Global Warming Potential of 1. See climate change and global warming. [5]

Carbon Dioxide Equivalent
A metric measure used to compare the emissions from various greenhouse gases based upon their global warming potential (GWP). Carbon dioxide equivalents are commonly expressed as "million metric tons of carbon dioxide equivalents (MMTCO2Eq)." The carbon dioxide equivalent for a gas is derived by multiplying the tons of the gas by the associated GWP.

MMTCO2Eq = (million metric tons of a gas) * (GWP of the gas)

See greenhouse gas, global warming potential, metric ton.

Carbon Dioxide Fertilization
The enhancement of the growth of plants as a result of increased atmospheric CO2 concentration. Depending on their mechanism of photosynthesis, certain types of plants are more sensitive to changes in atmospheric CO2 concentration. [1]

Carbon Footprint
The total amount of greenhouse gases that are emitted into the atmosphere each year by a person, family, building, organization, or company. A persons carbon footprint includes greenhouse gas emissions from fuel that an individual burns directly, such as by heating a home or riding in a car. It also includes greenhouse gases that come from producing the goods or services that the individual uses, including emissions from power plants that make electricity, factories that make products, and landfills where trash gets sent.

Carbon Sequestration
Terrestrial, or biologic, carbon sequestration is the process by which trees and plants absorb carbon dioxide, release the oxygen, and store the carbon. Geologic sequestration is one step in the process of carbon capture and sequestration (CCS), and involves injecting carbon dioxide deep underground where it stays permanently.

Carbon Capture and Sequestration
Carbon capture and sequestration (CCS) is a set of technologies that can greatly reduce carbon dioxide emissions from new and existing coal- and gas-fired power plants, industrial processes, and other stationary sources of carbon dioxide. It is a three-step process that includes capture of carbon dioxide from power plants or industrial sources; transport of the captured and compressed carbon dioxide (usually in pipelines); and underground injection and geologic sequestration, or permanent storage, of that carbon dioxide in rock formations that contain tiny openings or pores that trap and hold the carbon dioxide.

Chlorofluorocarbons
Gases covered under the 1987 Montreal Protocol and used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. Since they are not destroyed in the lower atmosphere, CFCs drift into the upper atmosphere where, given suitable conditions, they break down ozone. These gases are being replaced by other compounds: hydrochlorofluorocarbons, an interim replacement for CFCs that are also covered under the Montreal Protocol, and hydrofluorocarbons, which are covered under the Kyoto Protocol. All these substances are also greenhouse gases. See hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, ozone depleting substance. [2]

Climate
Climate in a narrow sense is usually defined as the "average weather," or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands of years. The classical period is 3 decades, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. See weather. [1]

Climate Change
Climate change refers to any significant change in the measures of climate lasting for an extended period of time. In other words, climate change includes major changes in temperature, precipitation, or wind patterns, among others, that occur over several decades or longer.

Climate Feedback
A process that acts to amplify or reduce direct warming or cooling effects.

Climate Lag
The delay that occurs in climate change as a result of some factor that changes only very slowly. For example, the effects of releasing more carbon dioxide into the atmosphere occur gradually over time because the ocean takes a long time to warm up in response to a change in radiation. See climate, climate change.

Climate Model
A quantitative way of representing the interactions of the atmosphere, oceans, land surface, and ice. Models can range from relatively simple to quite comprehensive. See General Circulation Model. [3]

Climate Sensitivity
In Intergovernmental Panel on Climate Change (IPCC) reports, equilibrium climate sensitivity refers to the equilibrium change in global mean surface temperature following a doubling of the atmospheric (equivalent) CO2 concentration. More generally, equilibrium climate sensitivity refers to the equilibrium change in surface air temperature following a unit change in radiative forcing (degrees Celsius, per watts per square meter, (C/Wm-2). One method of evaluating the equilibrium climate sensitivity requires very long simulations with Coupled General Circulation Models (Climate model). The effective climate sensitivity is a related measure that circumvents this requirement. It is evaluated from model output for evolving non-equilibrium conditions. It is a measure of the strengths of the feedbacks at a particular time and may vary with forcing history and climate state. See climate, radiative forcing. [1]

Climate System (or Earth System)
The five physical components (atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere) that are responsible for the climate and its variations. [3]

Coal Mine Methane
Coal mine methane is the subset of coalbed methane that is released from the coal seams during the process of coal mining. For more information, visit the Coalbed Methane Outreach program site.

Coalbed Methane
Coalbed methane is methane contained in coal seams, and is often referred to as virgin coalbed methane, or coal seam gas. For more information, visit the Coalbed Methane Outreach program site.

Co-Benefit
The benefits of policies that are implemented for various reasons at the same time including climate change mitigation acknowledging that most policies designed to address greenhouse gas mitigation also have other, often at least equally important, rationales (e.g., related to objectives of development, sustainability, and equity).

Concentration
Amount of a chemical in a particular volume or weight of air, water, soil, or other medium. See parts per billion, parts per million. [4]

Conference of the Parties
The supreme body of the United Nations Framework Convention on Climate Change (UNFCCC). It comprises more than 180 nations that have ratified the Convention. Its first session was held in Berlin, Germany, in 1995 and it is expected to continue meeting on a yearly basis. The COP's role is to promote and review the implementation of the Convention. It will periodically review existing commitments in light of the Convention's objective, new scientific findings, and the effectiveness of national climate change programs. See United Nations Framework Convention on Climate Change.

Coral Bleaching
The process in which a coral colony, under environmental stress expels the microscopic algae (zooxanthellae) that live in symbiosis with their host organisms (polyps). The affected coral colony appears whitened.

Cryosphere
One of the interrelated components of the Earth's system, the cryosphere is frozen water in the form of snow, permanently frozen ground (permafrost), floating ice, and glaciers. Fluctuations in the volume of the cryosphere cause changes in ocean sea level, which directly impact the atmosphere and biosphere. [3]

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D

Deforestation
Those practices or processes that result in the conversion of forested lands for non-forest uses. Deforestation contributes to increasing carbon dioxide concentrations for two reasons: 1) the burning or decomposition of the wood releases carbon dioxide; and 2) trees that once removed carbon dioxide from the atmosphere in the process of photosynthesis are no longer present. [4]

Desertification
Land degradation in arid, semi-arid, and dry sub-humid areas resulting from various factors, including climatic variations and human activities. Further, the UNCCD (The United Nations Convention to Combat Desertification) defines land degradation as a reduction or loss, in arid, semi-arid, and dry sub-humid areas, of the biological or economic productivity and complexity of rain-fed cropland, irrigated cropland, or range, pasture, forest, and woodlands resulting from land uses or from a process or combination of processes, including processes arising from human activities and habitation patterns, such as: (i) soil erosion caused by wind and/or water; (ii) deterioration of the physical, chemical and biological or economic properties of soil; and (iii) long-term loss of natural vegetation. Conversion of forest to non-forest.

Dryland Farming
A technique that uses soil moisture conservation and seed selection to optimize production under dry conditions.

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E

Eccentricity
The extent to which the Earth's orbit around the Sun departs from a perfect circle.

Ecosystem
Any natural unit or entity including living and non-living parts that interact to produce a stable system through cyclic exchange of materials. [3]

El Niño - Southern Oscillation (ENSO)
El Niño in its original sense, is a warm water current that periodically flows along the coast of Ecuador and Peru, disrupting the local fishery. This oceanic event is associated with a fluctuation of the intertropical surface pressure pattern and circulation in the Indian and Pacific Oceans, called the Southern Oscillation. This coupled atmosphere-ocean phenomenon is collectively known as El Niño-Southern Oscillation. During an El Niño event, the prevailing trade winds weaken and the equatorial countercurrent strengthens, causing warm surface waters in the Indonesian area to flow eastward to overlie the cold waters of the Peru current. This event has great impact on the wind, sea surface temperature, and precipitation patterns in the tropical Pacific. It has climatic effects throughout the Pacific region and in many other parts of the world. The opposite of an El Niño event is called La Niña. [6]

Emissions
The release of a substance (usually a gas when referring to the subject of climate change) into the atmosphere.

Emissions Factor
A unique value for scaling emissions to activity data in terms of a standard rate of emissions per unit of activity (e.g., grams of carbon dioxide emitted per barrel of fossil fuel consumed, or per pound of product produced). [4]

Energy Efficiency
Using less energy to provide the same service. [7]

ENERGY STAR
A U.S. Environmental Protection Agency voluntary program that helps businesses and individuals save money and protect our climate through superior energy efficiency. Learn more about ENERGY STAR.

Enhanced Greenhouse Effect
The concept that the natural greenhouse effect has been enhanced by increased atmospheric concentrations of greenhouse gases (such as CO2 and methane) emitted as a result of human activities. These added greenhouse gases cause the earth to warm. See greenhouse effect.

Enteric Fermentation
Livestock, especially cattle, produce methane as part of their digestion. This process is called enteric fermentation, and it represents one third of the emissions from the agriculture sector.

Evaporation
The process by which water changes from a liquid to a gas or vapor. [8]

Evapotranspiration
The combined process of evaporation from the Earth's surface and transpiration from vegetation. [1]

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F

Feedback Mechanisms
Factors which increase or amplify (positive feedback) or decrease (negative feedback) the rate of a process. An example of positive climatic feedback is the ice-albedo feedback. See climate feedback. [3]

Fluorinated Gases
Powerful synthetic greenhouse gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride that are emitted from a variety of industrial processes. Fluorinated gases are sometimes used as substitutes for stratospheric ozone-depleting substances (e.g., chlorofluorocarbons, hydrochlorofluorocarbons, and halons) and are often used in coolants, foaming agents, fire extinguishers, solvents, pesticides, and aerosol propellants. These gases are emitted in small quantities compared to carbon dioxide (CO2), methane (CH4), or nitrous oxide (N2O), but because they are potent greenhouse gases, they are sometimes referred to as High Global Warming Potential gases (High GWP gases).

Fluorocarbons
Carbon-fluorine compounds that often contain other elements such as hydrogen, chlorine, or bromine. Common fluorocarbons include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs). See chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, ozone depleting substance. [3]

Forcing Mechanism
A process that alters the energy balance of the climate system, i.e. changes the relative balance between incoming solar radiation and outgoing infrared radiation from Earth. Such mechanisms include changes in solar irradiance, volcanic eruptions, and enhancement of the natural greenhouse effect by emissions of greenhouse gases. See radiation, infrared radiation, radiative forcing.

Fossil Fuel
A general term for organic materials formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth's crust over hundreds of millions of years. [4]

Fuel Switching
In general, this is substituting one type of fuel for another. In the climate-change discussion it is implicit that the substituted fuel produces lower carbon emissions per unit energy produced than the original fuel, e.g., natural gas for coal.

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G

General Circulation Model (GCM)
A global, three-dimensional computer model of the climate system which can be used to simulate human-induced climate change. GCMs are highly complex and they represent the effects of such factors as reflective and absorptive properties of atmospheric water vapor, greenhouse gas concentrations, clouds, annual and daily solar heating, ocean temperatures and ice boundaries. The most recent GCMs include global representations of the atmosphere, oceans, and land surface. See climate modeling. [3]

Geosphere
The soils, sediments, and rock layers of the Earth's crust, both continental and beneath the ocean floors.

Glacier
A multi-year surplus accumulation of snowfall in excess of snowmelt on land and resulting in a mass of ice at least 0.1 km2 in area that shows some evidence of movement in response to gravity. A glacier may terminate on land or in water. Glacier ice is the largest reservoir of fresh water on Earth, and second only to the oceans as the largest reservoir of total water. Glaciers are found on every continent except Australia. [3]

Global Average Temperature
An estimate of Earths mean surface air temperature averaged over the entire planet.

Global Warming
The recent and ongoing global average increase in temperature near the Earths surface.

Global Warming Potential
A measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide.

Greenhouse Effect
Trapping and build-up of heat in the atmosphere (troposphere) near the Earths surface. Some of the heat flowing back toward space from the Earth's surface is absorbed by water vapor, carbon dioxide, ozone, and several other gases in the atmosphere and then reradiated back toward the Earths surface. If the atmospheric concentrations of these greenhouse gases rise, the average temperature of the lower atmosphere will gradually increase. See greenhouse gas, anthropogenic, climate, global warming. [4]

Greenhouse Gas (GHG)
Any gas that absorbs infrared radiation in the atmosphere. Greenhouse gases include, carbon dioxide, methane, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride. [4]

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H

Habitat Fragmentation
A process during which larger areas of habitat are broken into a number of smaller patches of smaller total area, isolated from each other by a matrix of habitats unlike the original habitat. (Fahrig 2003)

Halocarbons
Compounds containing either chlorine, bromine or fluorine and carbon. Such compounds can act as powerful greenhouse gases in the atmosphere. The chlorine and bromine containing halocarbons are also involved in the depletion of the ozone layer. [1]

Heat Island
An urban area characterized by temperatures higher than those of the surrounding non-urban area. As urban areas develop, buildings, roads, and other infrastructure replace open land and vegetation. These surfaces absorb more solar energy, which can create higher temperatures in urban areas. [8]

Heat Waves
A prolonged period of excessive heat, often combined with excessive humidity. [9]

Hydrocarbons
Substances containing only hydrogen and carbon. Fossil fuels are made up of hydrocarbons.

Hydrochlorofluorocarbons (HCFCs)
Compounds containing hydrogen, fluorine, chlorine, and carbon atoms. Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases. See ozone depleting substance.

Hydrofluorocarbons (HFCs)
Compounds containing only hydrogen, fluorine, and carbon atoms. They were introduced as alternatives to ozone depleting substances in serving many industrial, commercial, and personal needs. HFCs are emitted as by-products of industrial processes and are also used in manufacturing. They do not significantly deplete the stratospheric ozone layer, but they are powerful greenhouse gases with global warming potentials ranging from 140 (HFC-152a) to 11,700 (HFC-23).

Hydrologic Cycle
The process of evaporation, vertical and horizontal transport of vapor, condensation, precipitation, and the flow of water from continents to oceans. It is a major factor in determining climate through its influence on surface vegetation, the clouds, snow and ice, and soil moisture. The hydrologic cycle is responsible for 25 to 30 percent of the mid-latitudes' heat transport from the equatorial to polar regions. [3]

Hydrosphere
The component of the climate system comprising liquid surface and subterranean water, such as: oceans, seas, rivers, fresh water lakes, underground water etc. [1]

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I

Ice Core
A cylindrical section of ice removed from a glacier or an ice sheet in order to study climate patterns of the past. By performing chemical analyses on the air trapped in the ice, scientists can estimate the percentage of carbon dioxide and other trace gases in the atmosphere at a given time. Analysis of the ice itself can give some indication of historic temperatures.

Indirect Emissions
Indirect emissions from a building, home or business are those emissions of greenhouse gases that occur as a result of the generation of electricity used in that building. These emissions are called "indirect" because the actual emissions occur at the power plant which generates the electricity, not at the building using the electricity.

Industrial Revolution
A period of rapid industrial growth with far-reaching social and economic consequences, beginning in England during the second half of the 18th century and spreading to Europe and later to other countries including the United States. The industrial revolution marks the beginning of a strong increase in combustion of fossil fuels and related emissions of carbon dioxide. [8]

Infrared Radiation
Infrared radiation consists of light whose wavelength is longer than the red color in the visible part of the spectrum, but shorter than microwave radiation. Infrared radiation can be perceived as heat. The Earths surface, the atmosphere, and clouds all emit infrared radiation, which is also known as terrestrial or long-wave radiation. In contrast, solar radiation is mainly short-wave radiation because of the temperature of the Sun. See radiation, greenhouse effect, enhanced greenhouse effect, global warming. [1]

Intergovernmental Panel on climate Change (IPCC)
The IPCC was established jointly by the United Nations Environment Programme and the World Meteorological Organization in 1988. The purpose of the IPCC is to assess information in the scientific and technical literature related to all significant components of the issue of climate change. The IPCC draws upon hundreds of the world's expert scientists as authors and thousands as expert reviewers. Leading experts on climate change and environmental, social, and economic sciences from some 60 nations have helped the IPCC to prepare periodic assessments of the scientific underpinnings for understanding global climate change and its consequences. With its capacity for reporting on climate change, its consequences, and the viability of adaptation and mitigation measures, the IPCC is also looked to as the official advisory body to the world's governments on the state of the science of the climate change issue. For example, the IPCC organized the development of internationally accepted methods for conducting national greenhouse gas emission inventories.

Inundation
The submergence of land by water, particularly in a coastal setting. [10]

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L

Landfill
Land waste disposal site in which waste is generally spread in thin layers, compacted, and covered with a fresh layer of soil each day. [4]

Latitude
The location north or south in reference to the equator, which is designated at zero (0) degrees. Lines of latitude are parallel to the equator and circle the globe. The North and South poles are at 90 degrees North and South latitude. [11]

Least Developed Country
A country with low indicators of socioeconomic development and human resources, as well as economic vulnerability, as determined by the United Nations. [12]

Longwave Radiation
Radiation emitted in the spectral wavelength greater than about 4 micrometers, corresponding to the radiation emitted from the Earth and atmosphere. It is sometimes referred to as 'terrestrial radiation' or 'infrared radiation,' although somewhat imprecisely. See infrared radiation. [3]

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M

Megacities
Cities with populations over 10 million.

Methane (CH4)
A hydrocarbon that is a greenhouse gas with a global warming potential most recently estimated at 25 times that of carbon dioxide (CO2). Methane is produced through anaerobic (without oxygen) decomposition of waste in landfills, animal digestion, decomposition of animal wastes, production and distribution of natural gas and petroleum, coal production, and incomplete fossil fuel combustion. The GWP is from the IPCC's Fourth Assessment Report (AR4). For more information visit EPA's Methane page.

Metric Ton
Common international measurement for the quantity of greenhouse gas emissions. A metric ton is equal to 2205 lbs or 1.1 short tons. See short ton. [4]

Mitigation
A human intervention to reduce the human impact on the climate system; it includes strategies to reduce greenhouse gas sources and emissions and enhancing greenhouse gas sinks. [8]

Mount Pinatubo
A volcano in the Philippine Islands that erupted in 1991. The eruption of Mount Pinatubo ejected enough particulate and sulfate aerosol matter into the atmosphere to block some of the incoming solar radiation from reaching Earth's atmosphere. This effectively cooled the planet from 1992 to 1994, masking the warming that had been occurring for most of the 1980s and 1990s. [3]

Municipal Solid Waste (MSW)
Residential solid waste and some non-hazardous commercial, institutional, and industrial wastes. This material is generally sent to municipal landfills for disposal. See landfill.

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N

Natural Gas
Underground deposits of gases consisting of 50 to 90 percent methane (CH4) and small amounts of heavier gaseous hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

Natural Variability
Variations in the mean state and other statistics (such as standard deviations or statistics of extremes) of the climate on all time and space scales beyond that of individual weather events. Natural variations in climate over time are caused by internal processes of the climate system, such as El Niño as well as changes in external influences, such as volcanic activity and variations in the output of the sun. [8] [13]

Nitrogen Cycle
The natural circulation of nitrogen among the atmosphere, plants, animals, and microorganisms that live in soil and water. Nitrogen takes on a variety of chemical forms throughout the nitrogen cycle, including nitrous oxide (N2O) and nitrogen oxides (NOx).

Nitrogen Oxides (NOx)
Gases consisting of one molecule of nitrogen and varying numbers of oxygen molecules. Nitrogen oxides are produced in the emissions of vehicle exhausts and from power stations. In the atmosphere, nitrogen oxides can contribute to formation of photochemical ozone (smog), can impair visibility, and have health consequences; they are thus considered pollutants. [3]

Nitrous Oxide (N2O)
A powerful greenhouse gas with a global warming potential of 298 times that of carbon dioxide (CO2). Major sources of nitrous oxide include soil cultivation practices, especially the use of commercial and organic fertilizers, fossil fuel combustion, nitric acid production, and biomass burning. The GWP is from the IPCC's Fourth Assessment Report (AR4). [3]

Natural emissions of N2O are mainly from bacteria breaking down nitrogen in soils and the oceans. Nitrous oxide is mainly removed from the atmosphere through destruction in the stratosphere by ultraviolet radiation and associated chemical reactions, but it can also be consumed by certain types of bacteria in soils.

Non-Methane Volatile Organic Compounds (NMVOCs)
Organic compounds, other than methane, that participate in atmospheric photochemical reactions.

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O

Ocean Acidification
Increased concentrations of carbon dioxide in sea water causing a measurable increase in acidity (i.e., a reduction in ocean pH). This may lead to reduced calcification rates of calcifying organisms such as corals, mollusks, algae and crustaceans. [8]

Oxidize
To chemically transform a substance by combining it with oxygen. [4]

Ozone
Ozone, the triatomic form of oxygen (O3), is a gaseous atmospheric constituent. In the troposphere, it is created by photochemical reactions involving gases resulting both from natural sources and from human activities (photochemical smog). In high concentrations, tropospheric ozone can be harmful to a wide range of living organisms. Tropospheric ozone acts as a greenhouse gas. In the stratosphere, ozone is created by the interaction between solar ultraviolet radiation and molecular oxygen (O2). Stratospheric ozone plays a decisive role in the stratospheric radiative balance. Depletion of stratospheric ozone, due to chemical reactions that may be enhanced by climate change, results in an increased ground-level flux of ultraviolet (UV-) B radiation. See atmosphere, ultraviolet radiation. [6]

Ozone Depleting Substance (ODS)
A family of man-made compounds that includes, but are not limited to, chlorofluorocarbons (CFCs), bromofluorocarbons (halons), methyl chloroform, carbon tetrachloride, methyl bromide, and hydrochlorofluorocarbons (HCFCs). These compounds have been shown to deplete stratospheric ozone, and therefore are typically referred to as ODSs. See ozone. [4]

Ozone Layer
The layer of ozone that begins approximately 15 km above Earth and thins to an almost negligible amount at about 50 km, shields the Earth from harmful ultraviolet radiation from the sun. The highest natural concentration of ozone (approximately 10 parts per million by volume) occurs in the stratosphere at approximately 25 km above Earth. The stratospheric ozone concentration changes throughout the year as stratospheric circulation changes with the seasons. Natural events such as volcanoes and solar flares can produce changes in ozone concentration, but man-made changes are of the greatest concern. See stratosphere, ultraviolet radiation. [3]

Ozone Precursors
Chemical compounds, such as carbon monoxide, methane, non-methane hydrocarbons, and nitrogen oxides, which in the presence of solar radiation react with other chemical compounds to form ozone, mainly in the troposphere. See troposphere. [4]

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P

Particulate matter (PM)
Very small pieces of solid or liquid matter such as particles of soot, dust, fumes, mists or aerosols. The physical characteristics of particles, and how they combine with other particles, are part of the feedback mechanisms of the atmosphere. See aerosol, sulfate aerosols. [3]

Parts Per Billion (ppb)
Number of parts of a chemical found in one billion parts of a particular gas, liquid, or solid mixture. See concentration.

Parts Per Million by Volume (ppmv)
Number of parts of a chemical found in one million parts of a particular gas, liquid, or solid. See concentration.

Parts Per Trillion (ppt)
Number of parts of a chemical found in one trillion parts of a particular gas, liquid or solid. See concentration.

Perfluorocarbons (PFCs)
A group of chemicals composed of carbon and fluorine only. These chemicals (predominantly CF4 and C2F6) were introduced as alternatives, along with hydrofluorocarbons, to the ozone depleting substances. In addition, PFCs are emitted as by-products of industrial processes and are also used in manufacturing. PFCs do not harm the stratospheric ozone layer, but they are powerful greenhouse gases: CF4 has a global warming potential (GWP) of 7,390 and C2F6 has a GWP of 12,200. The GWP is from the IPCC's Fourth Assessment Report (AR4). These chemicals are predominantly human-made, though there is a small natural source of CF4. See ozone depleting substance.

Permafrost
Perennially (continually) frozen ground that occurs where the temperature remains below 0ºC for several years. [8]

Phenology
The timing of natural events, such as flower blooms and animal migration, which is influenced by changes in climate. Phenology is the study of such important seasonal events. Phenological events are influenced by a combination of climate factors, including light, temperature, rainfall, and humidity.

Photosynthesis
The process by which plants take CO2 from the air (or bicarbonate in water) to build carbohydrates, releasing O2 in the process. There are several pathways of photosynthesis with different responses to atmospheric CO2 concentrations. See carbon sequestration, carbon dioxide fertilization. [1]

Precession
The wobble over thousands of years of the tilt of the Earths axis with respect to the plane of the solar system. [3]

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R

Radiation
Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object. See ultraviolet radiation, infrared radiation, solar radiation, longwave radiation. [3]

Radiative Forcing
A measure of the influence of a particular factor (e.g. greenhouse gas (GHG), aerosol, or land use change) on the net change in the Earths energy balance.

Recycling
Collecting and reprocessing a resource so it can be used again. An example is collecting aluminum cans, melting them down, and using the aluminum to make new cans or other aluminum products. [4]

Reflectivity
The ability of a surface material to reflect sunlight including the visible, infrared, and ultraviolet wavelengths. [14]

Reforestation
Planting of forests on lands that have previously contained forests but that have been converted to some other use.[1]

Relative Sea Level Rise
The increase in ocean water levels at a specific location, taking into account both global sea level rise and local factors, such as local subsidence and uplift. Relative sea level rise is measured with respect to a specified vertical datum relative to the land, which may also be changing elevation over time. [10]

Renewable Energy
Energy resources that are naturally replenishing such as biomass, hydro, geothermal, solar, wind, ocean thermal, wave action, and tidal action. [5]

Residence Time
The average time spent in a reservoir by an individual atom or molecule. With respect to greenhouse gases, residence time refers to how long on average a particular molecule remains in the atmosphere. For most gases other than methane and carbon dioxide, the residence time is approximately equal to the atmospheric lifetime. [4]

Resilience
A capability to anticipate, prepare for, respond to, and recover from significant multi-hazard threats with minimum damage to social well-being, the economy, and the environment.

Respiration
The process whereby living organisms convert organic matter to CO2, releasing energy and consuming O2. [1]

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S

Salt Water Intrusion
Displacement of fresh or ground water by the advance of salt water due to its greater density, usually in coastal and estuarine areas. [10]

Scenarios
A plausible and often simplified description of how the future may develop based on a coherent and internally consistent set of assumptions about driving forces and key relationships.

Sea Surface Temperature
The temperature in the top several feet of the ocean, measured by ships, buoys and drifters. [13]

Sensitivity
The degree to which a system is affected, either adversely or beneficially, by climate variability or change. The effect may be direct (e.g., a change in crop yield in response to a change in the mean, range or variability of temperature) or indirect (e.g., damages caused by an increase in the frequency of coastal flooding due to sea level rise). [8]

Short Ton
Common measurement for a ton in the United States. A short ton is equal to 2,000 lbs or 0.907 metric tons. See metric ton.

Sink
Any process, activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas or aerosol from the atmosphere. [1]

Snowpack
A seasonal accumulation of slow-melting snow. [8]

Soil Carbon
A major component of the terrestrial biosphere pool in the carbon cycle. The amount of carbon in the soil is a function of the historical vegetative cover and productivity, which in turn is dependent in part upon climatic variables. [4]

Solar Radiation
Radiation emitted by the Sun. It is also referred to as short-wave radiation. Solar radiation has a distinctive range of wavelengths (spectrum) determined by the temperature of the Sun. See ultraviolet radiation, infrared radiation, radiation. [1]

Storm Surge
An abnormal rise in sea level accompanying a hurricane or other intense storm, whose height is the difference between the observed level of the sea surface and the level that would have occurred in the absence of the cyclone. [10]

Stratosphere
Region of the atmosphere between the troposphere and mesosphere, having a lower boundary of approximately 8 km at the poles to 15 km at the equator and an upper boundary of approximately 50 km. Depending upon latitude and season, the temperature in the lower stratosphere can increase, be isothermal, or even decrease with altitude, but the temperature in the upper stratosphere generally increases with height due to absorption of solar radiation by ozone. [3]

Stratospheric Ozone
See ozone layer.

Streamflow
The volume of water that moves over a designated point over a fixed period of time. It is often expressed as cubic feet per second (ft3/sec). [6]

Subsiding/Subsidence
The downward settling of the Earth's crust relative to its surroundings. [10]

Sulfate Aerosols
Particulate matter that consists of compounds of sulfur formed by the interaction of sulfur dioxide and sulfur trioxide with other compounds in the atmosphere. Sulfate aerosols are injected into the atmosphere from the combustion of fossil fuels and the eruption of volcanoes like Mt. Pinatubo. Sulfate aerosols can lower the Earth's temperature by reflecting away solar radiation (negative radiative forcing). General Circulation Models which incorporate the effects of sulfate aerosols more accurately predict global temperature variations. See particulate matter, aerosol, General Circulation Models. [3]

Sulfur Hexafluoride (SF6)
A colorless gas soluble in alcohol and ether, slightly soluble in water. A very powerful greenhouse gas used primarily in electrical transmission and distribution systems and as a dielectric in electronics. The global warming potential of SF6 is 22,800. This GWP is from the IPCC's Fourth Assessment Report (AR4). See Global Warming Potential. [4]

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T

Teragram
1 trillion (1012) grams = 1 million (106) metric tons.

Thermal Expansion
The increase in volume (and decrease in density) that results from warming water. A warming of the ocean leads to an expansion of the ocean volume, which leads to an increase in sea level. [8]

Thermohaline Circulation
Large-scale density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic the thermohaline circulation consists of warm surface water flowing northward and cold deep water flowing southward, resulting in a net poleward transport of heat. The surface water sinks in highly restricted sinking regions located in high latitudes. [1]

Trace Gas
Any one of the less common gases found in the Earth's atmosphere. Nitrogen, oxygen, and argon make up more than 99 percent of the Earth's atmosphere. Other gases, such as carbon dioxide, water vapor, methane, oxides of nitrogen, ozone, and ammonia, are considered trace gases. Although relatively unimportant in terms of their absolute volume, they have significant effects on the Earth's weather and climate. [3]

Troposphere
The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes (ranging from 9 km in high latitudes to 16 km in the tropics on average) where clouds and "weather" phenomena occur. In the troposphere temperatures generally decrease with height. See ozone precursors, stratosphere, atmosphere. [1]

Tropospheric Ozone (O3)
See ozone.

Tropospheric Ozone Precursors
See ozone precursors.

Tundra
A treeless, level, or gently undulating plain characteristic of the Arctic and sub-Arctic regions characterized by low temperatures and short growing seasons. [8]

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U

Ultraviolet Radiation (UV)
The energy range just beyond the violet end of the visible spectrum. Although ultraviolet radiation constitutes only about 5 percent of the total energy emitted from the sun, it is the major energy source for the stratosphere and mesosphere, playing a dominant role in both energy balance and chemical composition.
Most ultraviolet radiation is blocked by Earth's atmosphere, but some solar ultraviolet penetrates and aids in plant photosynthesis and helps produce vitamin D in humans. Too much ultraviolet radiation can burn the skin, cause skin cancer and cataracts, and damage vegetation. [3]

United Nations Framework Convention on Climate Change (UNFCCC)
The Convention on Climate Change sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change. It recognizes that the climate system is a shared resource whose stability can be affected by industrial and other emissions of carbon dioxide and other greenhouse gases. The Convention enjoys near universal membership, with 189 countries having ratified.
Under the Convention, governments:

  • gather and share information on greenhouse gas emissions, national policies and best practices
  • launch national strategies for addressing greenhouse gas emissions and adapting to expected impacts, including the provision of financial and technological support to developing countries
  • cooperate in preparing for adaptation to the impacts of climate change

The Convention entered into force on 21 March 1994. [4]

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V

Vulnerability
The degree to which a system is susceptible to, or unable to cope with, adverse effects of climate change, including climate variability and extremes. Vulnerability is a function of the character, magnitude, and rate of climate variation to which a system is exposed; its sensitivity; and its adaptive capacity. [15]

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W

Wastewater
Water that has been used and contains dissolved or suspended waste materials. [4]

Water Vapor
The most abundant greenhouse gas, it is the water present in the atmosphere in gaseous form. Water vapor is an important part of the natural greenhouse effect. While humans are not significantly increasing its concentration through direct emissions, it contributes to the enhanced greenhouse effect because the warming influence of greenhouse gases leads to a positive water vapor feedback. In addition to its role as a natural greenhouse gas, water vapor also affects the temperature of the planet because clouds form when excess water vapor in the atmosphere condenses to form ice and water droplets and precipitation. See greenhouse gas. [3]

Weather
Atmospheric condition at any given time or place. It is measured in terms of such things as wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation. In most places, weather can change from hour-to-hour, day-to-day, and season-to-season. Climate in a narrow sense is usually defined as the "average weather", or more rigorously, as the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years. The classical period is 30 years, as defined by the World Meteorological Organization (WMO). These quantities are most often surface variables such as temperature, precipitation, and wind. Climate in a wider sense is the state, including a statistical description, of the climate system. A simple way of remembering the difference is that climate is what you expect (e.g. cold winters) and 'weather' is what you get (e.g. a blizzard). See climate.

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#

100-Year Flood Levels
Severe flood levels with a one-in-100 likelihood of occurring in any given year.

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1  IPCC Third Assessment Report Working Group I: The Scientific Basis EXIT
2  IPCC Third Assessment Report Working Group III: Mitigation EXIT
3  NASA's Earth Observatory library
4  UNFCCC glossaries EXIT
5  Energy Information Administration's Energy Glossary
6  IPCC Third Assessment Report Working Group II: Impacts, Adaptation and Vulnerability EXIT
7  Energy Information Administration's Energy Efficiency Glossary
8  IPCC Fourth Assessment Report Working Group II: Impacts, Adaptation, and Vulnerability EXIT
9  FEMA Extreme Heat Glossary
10  US Climate Change Science Program. Coastal Sensitivity to Sea Level Rise: A Focus on the Mid-Atlantic Region
11  National Weather Service Glossary
12  UN LDC criteria EXIT 
13  IPCC Fourth Assessment Report Working Group 1: The Physical Science Basis EXIT
14  EPA Heat Island Effect Glossary
15  US Climate Change Science Program. Preliminary Review of Adaptation Options for Climate Sensitive Ecosystems and Resources

climate action together.

Weather refers to atmospheric conditions at a particular time in a particular location, including temperature, humidity, precipitation, cloudiness, wind, and visibility. Weather conditions do not happen in isolation, they have a ripple effect. The weather in one region will eventually affect the weather hundreds or thousands of kilometers away.

Climate is the average of weather patterns in a specific area over a longer period of time, usually 30 or more years, that represents the overall state of the climate system.

Human activity in the industrial age, and particularly during the last century, is significantly altering our planet’s climate through the release of harmful greenhouse gases.

Greenhouse gases are gases that trap heat from the sun in our planet’s atmosphere, keeping it warm. Since the industrial era began, human activities have led to the release of dangerous levels of greenhouse gases, causing global warming and climate change.

The main greenhouse gases released by human activities are carbon dioxide, methane, nitrous oxide, and fluorinated gases used for cooling and refrigeration. Carbon dioxide is the primary greenhouse gas resulting from human activities, particularly from burning fossil fuels, deforestation, and changing the way land is used. Our reliance on fossil fuels has led to a 50 percent increase in the concentrations of carbon dioxide in the atmosphere over the last 200 years. Methane is another important greenhouse gas that is responsible for 25 percent of global warming. Methane is released during the extraction and transport of coal, gas, and oil, and by waste landfills and agricultural practices.

To prevent catastrophic climate change, the world’s governments must work together to significantly reduce greenhouse gas emissions now and in the coming decades and keep global warming below the dangerous threshold of 1.5°C.

Global warming is an increase in the Earth’s average surface temperature that occurs when the concentration of greenhouse gases in the atmosphere increases. These gases absorb more solar radiation and trap more heat, thus causing the planet to get hotter. Burning fossil fuels, cutting down forests, and farming livestock are some human activities that release greenhouse gases and contribute to global warming.

Climate change refers to the long-term changes in the Earth’s climate that are warming the atmosphere, ocean and land. Climate change is affecting the balance of ecosystems that support life and biodiversity, and impacting health. It also causes more extreme weather events, such as more intense and/or frequent hurricanes, floods, heat waves, and droughts, and leads to sea level rise and coastal erosion as a result of ocean warming, melting of glaciers, ad loss of ice sheets.

The climate crisis refers to the serious problems that are being caused, or are likely to be caused, by changes in the planet’s climate, including weather extremes and hazards, ocean acidification and sea-level rise, loss of biodiversity, food and water insecurity, health risks, economic disruption, displacement, and even violent conflict.

Since the 1800s, human activities have caused the Earth’s average temperature to increase by about 1.2° C – with more than two-thirds of this warming occurring since 1975. This is already causing significant damage to human societies and natural ecosystems in many parts of the world. More than 3 billion people live in places that are very vulnerable to the climate crisis, with lower income countries being disproportionately affected.

Scientists expect that an increase beyond 1.5°C would begin to lead to a series of dangerous tipping points that would make many changes irreversible and pose a very serious threat to human civilization. This is why governments must act now to drastically reduce greenhouse gas emissions and chart a course for reaching net zero in the coming decades, invest in adaptation to the unavoidable impacts of climate change, and protect and restore natural ecosystems and biomes upon which the planet depends.

Climate feedback loops happen when one change in the climate triggers further changes, in a chain reaction that reinforces itself as time goes on. Ultimately, feedback loops can trigger tipping points, at which point the changes to our planet’s climate systems become severe and irreversible.

Currently, scientists are aware of some serious feedback loops that are driving global warming. For example, as sea ice in the Arctic melts, more heat is being absorbed by the darker ocean waters, thus speeding up the warming process and leading to more ice melting. Similarly, as wildfires burn down forests, they release greenhouse gases leading to more warming and more wildfires. Other feedback loops include the thawing of the permafrost, forest dieback, and insect outbreaks.

A tipping point is a threshold after which certain changes caused by global warming and climate change become irreversible, even if future interventions are successful in driving down average global temperatures. These changes may lead to abrupt and dangerous impacts with very serious implications for the future of humanity and our planet.

As the world gets hotter, several tipping points are becoming very likely. One of them is the collapse of the Greenland and West Antarctic ice sheets, which would lead to significant sea level rise and threaten coastal communities and ecosystems. Another is the thawing of the permafrost in the tundra regions, which will release huge quantities of trapped greenhouse gases, further accelerating global warming and climate change. Mass coral bleaching events and the destruction of rainforests are two other major tipping points with immense implications for both biodiversity and human societies.

Under the Paris Agreement, countries are expected to take the necessary measures to avoid dangerous climate change by limiting global warming to well below 2°C, and pursuing efforts to limit it to 1.5°C. But even best-case scenarios now indicate a significant chance of overshooting these goals, even if temporarily. Climate overshoot refers to the period during which warming will have increased past 1.5° C, before falling back down. This period will probably occur around the middle of this century, but troubling signs are emerging that it may occur even earlier.

The longer the climate overshoot lasts, the more dangerous the world will become. A prolonged period of higher global temperatures will have devastating and irreversible impacts on natural ecosystems, biodiversity, and human communities, particularly in dry areas, coastal zones, and other vulnerable locations. Making deep emission cuts during this decade is of extreme importance to limiting the duration and impacts of the climate overshoot.

Climate change mitigation refers to any action taken by governments, businesses, or people to reduce or prevent greenhouse gas emissions, or to enhance carbon sinks that remove these gases from the atmosphere.

Reducing or preventing greenhouse gas emissions can be achieved by transitioning to renewable energy sources like wind and solar, using energy more efficiently, adopting low carbon or carbon-free transportation modalities, promoting sustainable agriculture and land use, and changing production and consumption models and diet behaviours. Enhancing carbon sinks can be achieved by restoring forests, wetlands, and marshlands, maintaining soil health, and protecting terrestrial and marine ecosystems.

In order for mitigation actions to be successful, it is crucial that countries develop supportive environments through legislation, policies, and investments.

Did you know: To limit global warming to 1.5° C, which is the critical goal of the Paris Agreement, the world must implement climate change mitigation actions to reduce greenhouse gas emissions by 45 percent before 2030 and reach net-zero by mid-century.

Climate change adaptation refers to actions that help reduce vulnerability to the current or expected impacts of climate change like weather extremes and hazards, sea-level rise, biodiversity loss, or food and water insecurity.

Even in very positive scenarios in which we manage to significantly and swiftly cut greenhouse gas emissions, climate change will continue to impact our world for decades to come because of the energy already trapped in the system. This means widespread adaptation is needed to limit these impacts and safeguard people and nature.

Many adaptation measures need to happen at the local level, so rural communities and cities have a big role to play. Such measures include planting crop varieties that are more resistant to drought and practicing regenerative agriculture, improving water storage and use, managing land to reduce wildfire risks, and building stronger defenses against extreme weather like floods and heat waves.

However, adaptation also needs to be driven at the national and international levels. In addition to developing the policies needed to guide adaptation, governments need to look at large-scale measures such as strengthening or relocating infrastructure from coastal areas affected by sea-level rise, building infrastructure able to withstand more extreme weather conditions, enhancing early warning systems and access to disaster information, developing insurance mechanisms specific to climate-related threats, and creating new protections for wildlife and natural ecosystems.

Climate resilience is the capacity of a community or environment to anticipate and manage climate impacts, minimize their damage, and recover and transform as needed after the initial shock.

To best safeguard societal wellbeing, economic activity, and the environment, people, communities, and governments need to be equipped to deal with the unavoidable impacts of climate change. This can be done by training people to obtain new skills and diversify the sources of their household income, building more robust disaster response and recovery capacities, enhancing climate information and early warning systems, and working on long-term planning, among others.

Ultimately, a truly climate-resilient society is a low-carbon one, because drastically reducing greenhouse gas emissions is the best way to limit how severe climate impacts will be in the future. It is also a society based in equity and climate justice that prioritizes support for people and communities most exposed to climate impacts or least able to cope with them.

A carbon footprint is a measure of the greenhouse gas emissions released into the atmosphere by a particular person, organization, product, or activity. A bigger carbon footprint means more emissions of carbon dioxide and methane, and therefore a bigger contribution to the climate crisis.

Measuring a person’s or an organization’s carbon footprint entails looking at both the direct emissions resulting from the burning of fossil fuels for energy production, heating, and land and air travel, and indirect emissions resulting from the production and disposal of all food, manufactured goods, and services they consume.

Carbon footprints can be reduced by shifting to low-carbon energy sources like wind and solar, improving energy efficiency, strengthening industry policies and regulations, changing purchasing and travel habits, and reducing meat consumption and food waste.

Climate justice means putting equity and human rights at the core of decision-making and action on climate change.

One aspect of climate justice relates to the unequal historical responsibility that countries bear in relation to the climate crisis. The concept suggests that the countries, industries, and businesses that have become wealthy from activities that emitted the most greenhouse gas emissions have a responsibility to help mitigate the impacts of climate change on those affected, particularly the most vulnerable countries and communities, who often are the ones that have contributed the least to the crisis.

Even within the same country, because of structural inequalities based on race, ethnicity, gender, and socioeconomic status, the responsibilities in addressing climate change need to be divided fairly, with the biggest responsibility resting on those who have contributed to, and benefitted from, causing the crisis the most.

Another aspect of climate justice is the intergenerational one. Children and young people today have not contributed to the climate crisis in a significant way but will bear the full force of climate change impacts as they advance through life. Because their human rights are threatened by the decisions of previous generations, they must have a central role in all climate decision-making and action.

Nature-based solutions are actions to protect, conserve, restore, and sustainably use and manage ecosystems to support climate change adaptation and mitigation efforts, preserve biodiversity, and enable sustainable livelihoods. They are actions that prioritize the importance of ecosystems and biodiversity and are designed and implemented with the full engagement and consent of local communities and Indigenous Peoples, who hold generational knowledge on protecting nature.

Nature-based solutions are used in many ways, across terrestrial, freshwater, coastal, and marine ecosystems. Restoring wetlands protects communities from floods, while conserving mangrove forests supports food sources and minimizes the impact of storms. Forests absorb carbon dioxide, allow biodiversity to thrive, increase water security, and combat landslides, while urban parks and gardens help cool down cities and limit the impact of heatwaves. Regenerative agriculture practices increase the amount of carbon captured by the soil and restore its health and productivity.

Nature-based solutions are seen as a win-win for people and nature, addressing multiple problems at once. They can create jobs, provide new and more resilient livelihood opportunities, and increase income while also protecting the planet and addressing climate change.

Indigenous Peoples’ ways of life are inherently low-carbon and emphasize balance between humans and the natural world. Their traditional practices have low impact on the environment and are responsive to it, fostering self-sustaining ecosystems.

Indigenous Peoples were among the first to notice climate change and their knowledge and practices help navigate and adapt to its impacts. Indigenous knowledge, which is intergenerational and community-based, is a great source of meaningful climate solutions that can advance mitigation, enhance adaptation, and build resilience. It can also complement scientific data with precise landscape information that is critical to evaluating climate change scenarios.

Indigenous Peoples protect an estimated 80 percent of the world’s remaining biodiversity yet continue to be largely excluded from almost all global decision-making processes on climate change. Their collective knowledge, valuable insights, and rights to their ancestral lands, territories and resources, and their way of life must be recognized and included across climate policies and actions.

There is no agreed definition of "Loss and damage" in the international climate negotiations. However, the term can refer to the unavoidable impacts of climate change that occur despite, or in the absence of, mitigation and adaptation. Importantly, it highlights that there are limits to what adaptation can accomplish; when tipping point thresholds are crossed, climate change impacts can become unavoidable.

Loss and damage can refer to both economic and non-economic losses. Economic loss and damage can include things like the costs of rebuilding infrastructure that has repeatedly been damaged due to cyclones or floods, or the loss of coastline land (and homes and businesses) due to sea-level rise and coastal erosion.

Non-economic loss and damage include negative impacts that can’t be easily assigned a monetary value. This can include things such as trauma from experiencing weather extremes and hazards, loss of life, the displacement of communities, loss of history and culture or loss of biodiversity.

Climate change can exacerbate food, water, and livelihood insecurity, with cascading effects such as displacement and migration and increased competition over natural resources, all of which can lead to increased tensions and instability in a country or a region. Furthermore, the impacts of climate change can aggravate or prolong existing violent conflicts and make it more difficult to deliver climate action and to reach and sustain peace. 

Climate security refers to evaluating, managing, and reducing the risks to peace and stability brought on by the climate crisis. This means ensuring that climate mitigation and adaptation goes beyond doing no harm and contributes positively to peace and stability. It also means that conflict prevention and peacebuilding interventions take climate impacts into account. The technical solutions to climate action and adaptation can serve as opportunities to build peace and mend the social fabric, especially in countries affected by conflict and fragility.

Did you know: Climate action can help alleviate the underlying drivers of conflict and fragility. For example, access to renewable energy can be a lifeline which supports clean water, light, warmth, and sustenance, as well as basic and emergency services. It also powers local economic development, while setting countries on a sustainable development pathway to recovery.

Climate finance refers to financial resources and instruments that are used to support action on climate change. Climate finance is critical to addressing climate change because of the large-scale investments that are needed to transition to a low-carbon global economy and to help societies build resilience and adapt to the impacts of climate change.

Climate finance can come from different sources, public or private, national or international, bilateral or multilateral. It can employ different instruments such as grants and donations, green bonds, debt swaps, guarantees, and concessional loans. And it can be used for different activities, including mitigation, adaptation, and resilience-building.

Some multilateral funds that countries can access include the Green Climate Fund (GCF), the Global Environment Facility (GEF), and the Adaptation Fund (AF). High-income countries with a significant historical contribution to climate change have committed to raising US$100 billion every year to fund climate action in low-income countries. However, this target has not yet been reached and more funding is required for both mitigation and adaptation interventions.

Did you know: Many studies and reports show that investments in climate action can yield results that dramatically outweigh the upfront costs. One study by the World Bank shows that an investment of US$1 can yield, on average, $4 in benefits.

Reaching net zero requires us to ensure that carbon dioxide emissions from human activity are balanced by human efforts to remove carbon dioxide emissions (for example, by creating carbon sinks to absorb carbon dioxide) - thereby stopping further increases in the concentration of greenhouse gases in the atmosphere. 

Transitioning to net zero requires a complete transformation of our energy, transportation, and production and consumption systems. This is necessary to avert the worst consequences of climate change.

Did you know: To keep global warming below 1.5°C, the world’s governments need to ensure that all greenhouse gas emissions peak by 2025, and reach net zero in the second half of this century. The IPCC has recommended to reduce CO2 emissions globally by 45% before 2030 (compared to 2010 levels) and reach net zero by mid-century.

Decarbonization means reducing the amount of greenhouse gas emissions that a society produces, as well as increasing the amount that is being absorbed. It entails changing many, if not all, aspects of the economy, from how energy is generated, to how goods and services are produced and delivered, to how buildings are built and how lands are managed.

To meet the goals of the Paris Agreement and keep the 1.5° target alive, governments and businesses must rapidly decarbonize by 2030. Meaningful decarbonization requires substantial investments in low-carbon infrastructure and transportation, renewable energy sources, circular economy and resource efficiency, and land and soil restoration. It also requires a rethinking of current economic models that are focused on growth at all costs.

Renewable energy is energy derived from natural sources that are constantly being replenished, such as wind, sunlight, the flow of moving water, and geothermal heat. In contrast to energy sourced from fossil fuels like coal, oil, and gas, which accounts for 75 percent of the harmful greenhouse gas emissions that are causing climate change, energy from renewable sources is cheap, clean, sustainable, and generates more jobs.

Transitioning from fossil fuels to renewable energy in all sectors – power, heating and cooling, transportation, and industry – is key to addressing the climate crisis. To stay under 1.5°C of global warming, the world needs to immediately phase out fossil fuel use and undergo a profound transformation of the energy system through rapid electrification and sourcing energy from renewable sources.

Did you know: In 2022, renewable sources provided 29 percent of global electricity. With the right investments, electricity from renewable sources could provide 65 percent of the world’s total electricity supply by 2030.

A carbon sink is any process, activity, or mechanism that absorbs more carbon dioxide from the atmosphere than it releases. Forests, oceans, and soil are the world’s largest natural carbon sinks.

Oceans absorb carbon dioxide from the atmosphere through marine ecosystems and the plant and animal life they harbor. Sequestering carbon in marine ecosystems is generally referred to as blue carbon. Forests and soil are the other main natural carbon sinks of the planet, storing carbon in trees and vegetation, wetlands and peat bogs, and plant litter.

Today, human activity, like burning fossil fuels and deforestation, causes more carbon to be released into the atmosphere than the Earth’s natural carbon sinks can absorb, leading to global warming and climate change. Human activities and climate change are also causing the degradation of these natural carbon sinks, threatening the release of the carbon they store back into the atmosphere. Therefore, protecting carbon sinks and expanding their capability to absorb carbon and store it long-term is a key strategy for tackling climate change and stabilizing the climate.

Carbon removal is the process of removing greenhouse gas emissions from the atmosphere, through natural solutions such as reforestation and soil management or technological solutions like direct air capture and enhanced mineralization. Carbon removal is not a substitute for cutting greenhouse gas emissions, but it can slow down climate change and is necessary to shorten any period during which we temporarily overshoot our climate targets.

Carbon capture and storage is the process of trapping carbon emissions produced by fossil fuel power plants or other industrial processes before they can enter our atmosphere by storing them deep underground. Carbon capture and storage should not be seen as an alternative to the green energy transition, but it has been proposed as a way to tackle emissions from sectors that are difficult to decarbonize, particularly heavy industries like cement, steel, and chemicals.

However, these technologies are only in the early development stage and will require carefully-designed policies. Dramatically slashing greenhouse gas emissions must remain the top priority to combat the climate crisis.

Carbon markets are trading schemes that create financial incentives for activities that reduce or remove greenhouse gas emissions. In these schemes, emissions are quantified into carbon credits that can be bought and sold. One tradable carbon credit equals one tonne of carbon dioxide, or the equivalent amount of a different greenhouse gas reduced, sequestered or avoided.

Carbon credits can be bought by countries as part of their NDC strategy, by corporations with sustainability targets, and by private individuals that want to compensate for their carbon footprint.

The supply of carbon credits comes from private entities or governments that develop programmes to reduce or remove emissions. These programmes are certified by a third party and registered under a carbon market standard.

For carbon markets to be successful, countries must work together to secure robust carbon accounting, ensure transparency for carbon market transactions, implement safeguards against human rights abuses and other adverse societal impacts, and combat greenwashing and the misrepresentation of carbon-neutral products and services.

Regenerative agriculture is a way of farming that nurtures and restores soil health, and therefore reduces water use, prevents land degradation, and promotes biodiversity. By minimizing land ploughing, practicing rotating crops, and using animal manure and compost, regenerative agriculture ensures that the soil stores more carbon, conserves more moisture, and is healthier due to thriving fungal communities.

Intensive agriculture is responsible for a third of global greenhouse gas emissions, uses 70 percent of the fresh water we consume, and leads to soil degradation through its use of heavy machinery, chemical fertilizers, and pesticides. It is also the biggest contributor to biodiversity loss. By contrast, regenerative agriculture helps lower greenhouse gas emissions, conserves water, and restores land. Moreover, healthy soil produces more food and better nutrition and has other positive impacts on ecosystems and biodiversity.

Forests provide immense benefits by removing carbon dioxide and pollutants from the atmosphere, preventing soil erosion, filtering water, and housing half of the world’s land species of animals, plants and insects. Reforestation and afforestation are two of the most effective nature-based solutions in fighting climate change and limiting its impacts.

Reforestation is the process of replanting trees in areas that had recent tree cover but where forests were lost, due to wildfires, drought, disease, or human activity such as agricultural clearing.

Afforestation is the process of planting trees in areas that have not been forested in recent history. Afforestation helps restore abandoned and degraded agricultural lands, prevent desertification, create carbon sinks, and generate new economic opportunities for local communities.

Rewilding is the mass restoration of ecosystems that have been damaged by human activity. More than conservation, which focuses on saving specific species through dedicated human intervention, rewilding refers to setting aside large areas for the natural world to regenerate in on its own terms. This sometimes requires the reintroduction of key species that have been driven extinct in a particular region, such as beavers, wolves, or large herbivores, who help shape entire ecosystems.

Rewilding can help combat climate change by removing more carbon dioxide from the atmosphere through healthy natural processes such as natural woodland regeneration. It also helps prevent species extinction by creating nature-rich habitats that allow wildlife to adapt to climate change and migrate as warming intensifies.

Circular economy refers to models of production and consumption that minimize waste and reduce pollution, promote sustainable uses of natural resources, and help regenerate nature.

Circular economy approaches are all around us. They can be employed in a number of different sectors from textiles to buildings and construction, and at various stages of a product’s lifecycle, including design, manufacturing, distribution, and disposal.

Besides helping tackle the problem of pollution, circular economy approaches can play a critical role in solving other complex challenges such as climate change and biodiversity loss. They can help countries accelerate their transition to more resilient and lower-carbon economies while also creating new green jobs.

Did you know: Currently, only 7.2 percent of used materials are cycled back into our economies after use. This has a significant burden on the environment and contributes to the climate, biodiversity, and pollution crises. As a result, we currently need about 1.7 Earths to deliver on all the world's resource demands.

The world’s oceans – their temperature, chemistry, currents, and life – drive global systems that make Earth habitable for humankind. Our rainwater, drinking water, weather, climate, coastlines, much of our food, medicines and even the oxygen in the air we breathe, are all provided and regulated by the seas. However, because of climate change, the health of our oceans is now at significant risk.

The "blue economy" concept seeks to promote economic development, social inclusion, and the preservation or improvement of livelihoods while at the same time ensuring environmental sustainability of the oceans and coastal areas.

Blue economy has diverse components, including established traditional ocean industries such as fisheries, tourism, and maritime transport, but also new and emerging activities, such as offshore renewable energy, aquaculture, seabed extractive activities, and marine biotechnology.

Green jobs are decent jobs that contribute to protecting and restoring the environment and addressing climate change. Green jobs can be found in both the production of green products and services, such as renewable energy, and in environmentally friendly processes, such as recycling. Green jobs help improve energy and raw material efficiency, limit greenhouse gas emissions, minimize waste and pollution, protect and restore ecosystems, and support adaptation to the impacts of climate change.

As the market for green jobs is expanding, countries must ensure that the workforce is equipped with the specific skills and education required to carry them out. This can be achieved by investing in training young people for future green jobs and by retraining workers from carbon-intensive industries. The latter is a key part of ensuring countries are pursuing a just transition and leave no one behind.

With public pressure to address the climate crisis rising, private sector companies are joining the transition to a low-carbon global economy. However, their efforts can sometimes turn into more of a marketing exercise than real, meaningful action.

Greenwashing refers to situations where a company makes misleading claims about their positive environmental impact or the sustainability of their products and services to convince consumers that they are acting on climate change. In some cases, greenwashing can be unintentional, because of lack of knowledge on environmental issues. However, it can also be carried out intentionally as a marketing and public relations exercise, exploiting public support towards environmental policies for profit.

Greenwashing can erode public confidence in sustainability and allow negative environmental impacts to continue unabated.

In the context of climate change, transitioning to a low-carbon or net-zero economy requires massive transformation of our economic systems. Such transformation runs the risk of further increasing social inequality, exclusion, civil unrest, and less competitive businesses, sectors, and markets.

As countries work to meet their climate goals, it’s vital that they ensure the whole-of-society – all communities, all workers, all social groups – are brought along and part of the structural change that takes place.

Ensuring a just transition means that countries choose to green their economy through transition pathways and approaches that reinforce equality and inclusivity. This means looking at the impacts of the transition on different groups of workers across the economy and providing opportunities for training and reskilling that support decent work and aim to leave no one behind.

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty adopted in 1992 to combat dangerous human interference with the climate system. It entered into force in 1994 and enjoys near universal membership, having been signed by 198 parties. It is the parent treaty of both the Paris Agreement and the Kyoto Protocol.

The UNFCCC secretariat is the United Nations entity tasked with supporting the global response to the threat of climate change. The secretariat facilitates intergovernmental climate change negotiations by organizing between two and four negotiating sessions each year, the largest and most important of which is the Conference of the Parties (COP). It also provides technical expertise and assists in the analysis and review of climate change information and maintains the registry of Nationally Determined Contributions (NDC).

The annual United Nations conference dedicated to climate change, called the “Conference of the Parties” or “COP,” has been organized under the UN Framework Convention on Climate Change (UNFCCC) since 1995. At the 21st COP, or COP21, which took place in 2015, the Paris Agreement was signed.

The conference now brings together all nations who are parties to the Paris Agreement to discuss their next steps to combat climate change and further establish legally binding agreements to support climate action.

The Paris Agreement is a legally binding international treaty aiming to limit global warming to well below 2° C, preferably to 1.5° C, compared to pre-industrial levels. It was adopted by 196 Parties in 2015 at COP21 in Paris and entered into force in 2016.

The Paris Agreement is a landmark achievement in international cooperation on climate change because it is a binding agreement for all Parties to scale up efforts to combat climate change and adapt to its effects. It also provides the instruments for developed nations to assist developing nations in their climate mitigation and adaptation efforts, while creating a framework for transparent monitoring and reporting of results.

Nationally Determined Contributions (NDCs) are climate pledges and action plans that each country is required to develop in line with the Paris Agreement goal of limiting global warming to 1.5° C. NDCs represent short to medium-term plans that are updated every five years with higher ambition on climate.

NDCs outline mitigation and adaptation priorities a country will pursue to reduce greenhouse gas emissions, build resilience, and adapt to climate change, as well as financing strategies and monitoring and verification approaches. In 2023, the first in a series of global “stock takes” will conclude that assesses progress on the implementation of NDCs and Paris Agreement goals.

Under the Paris Agreement, countries must regularly report on the implementation of their Nationally Determined Contributions. It is crucial that this reporting is done with transparency to allow the global community to accurately assess collective progress and build trust that everyone is playing their part.

Transparent reporting allows governments and international bodies to have access to reliable data and make evidence-based decisions. It also enhances our scientific understanding of climate change and the actions and policies needed to mitigate it and adapt to its impacts. Ultimately, transparency is key to unlocking the full potential of the Paris Agreement, by promoting trust, collaboration and knowledge transfer and encouraging further ambition on climate targets.

National Adaptation Plans (NAPs) help countries plan and implement actions to reduce vulnerability to the impacts of climate change and strengthen adaptive capacity and resilience. NAPs link to Nationally Determined Contributions (NDCs) and other national and sectoral policies and programmes.

For NAPs to be successful they need to be participatory, inclusive, gender-responsive, and transparent. This means that at the design stage, NAPs need to evaluate the specific needs and vulnerabilities of different groups in the country, paying particular attention to those most vulnerable to climate change impacts and involving them in developing and implementing strategies and programmes.

Under the Paris Agreement, countries are invited to communicate long-term strategies (LTS) for emissions reductions that envision a whole-of-society transformation over several decades, usually up to 2050. LTS documents align to the long-term objectives of limiting global warming and achieving net-zero by 2050.

Long-term strategies provide a long-term vision that gives coherence and direction to shorter-term national climate pledges like the NDCs. They guide countries to pursue low-carbon development and prevent fossil fuel-intensive investments, demonstrating the socio-economic benefits of the green transition. They boost innovation and can help drive investment in low-carbon solutions and sustainable infrastructure. And they help facilitate and promote just and equitable transitions for the people who are most affected, making sure that climate solutions are fair and inclusive.

When countries officially communicate their LTS to the UNFCCC it is called a Long-Term Low Emission Development Strategy (LT-LEDS). All submissions can be accessed on the UNFCCC website.

Forest conservation and restoration can provide more than one quarter of the greenhouse gas emissions reductions needed to avoid the worst impacts of climate change. REDD+ is a framework agreed by countries in the international climate negotiations that aims to curb climate change by reducing deforestation and forest degradation, and sustainably managing and conserving forests in developing countries.

REDD stands for "Reducing Emissions from Deforestation and forest Degradation”. The “+” signifies the role of conservation, sustainable management of forests and enhancement of forest carbon stocks.

The Intergovernmental Panel on Climate Change (IPCC) is an independent body founded under the auspices of the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).

The IPCC’s main role is to assess the scientific literature and findings on climate change and provide vital scientific information and evidenced-based recommendations to policymakers and the public. It is widely recognized as the most credible source of information related to the science of climate change and its complex analysis of impacts, risks, and adaptation and mitigation options.

climate action together.

Weather refers to atmospheric conditions at a particular time in a particular location, including temperature, humidity, precipitation, cloudiness, wind, and visibility. Weather conditions do not happen in isolation, they have a ripple effect. The weather in one region will eventually affect the weather hundreds or thousands of kilometers away.

Climate is the average of weather patterns in a specific area over a longer period of time, usually 30 or more years, that represents the overall state of the climate system.

Human activity in the industrial age, and particularly during the last century, is significantly altering our planet’s climate through the release of harmful greenhouse gases.

Greenhouse gases are gases that trap heat from the sun in our planet’s atmosphere, keeping it warm. Since the industrial era began, human activities have led to the release of dangerous levels of greenhouse gases, causing global warming and climate change.

The main greenhouse gases released by human activities are carbon dioxide, methane, nitrous oxide, and fluorinated gases used for cooling and refrigeration. Carbon dioxide is the primary greenhouse gas resulting from human activities, particularly from burning fossil fuels, deforestation, and changing the way land is used. Our reliance on fossil fuels has led to a 50 percent increase in the concentrations of carbon dioxide in the atmosphere over the last 200 years. Methane is another important greenhouse gas that is responsible for 25 percent of global warming. Methane is released during the extraction and transport of coal, gas, and oil, and by waste landfills and agricultural practices.

To prevent catastrophic climate change, the world’s governments must work together to significantly reduce greenhouse gas emissions now and in the coming decades and keep global warming below the dangerous threshold of 1.5°C.

Global warming is an increase in the Earth’s average surface temperature that occurs when the concentration of greenhouse gases in the atmosphere increases. These gases absorb more solar radiation and trap more heat, thus causing the planet to get hotter. Burning fossil fuels, cutting down forests, and farming livestock are some human activities that release greenhouse gases and contribute to global warming.

Climate change refers to the long-term changes in the Earth’s climate that are warming the atmosphere, ocean and land. Climate change is affecting the balance of ecosystems that support life and biodiversity, and impacting health. It also causes more extreme weather events, such as more intense and/or frequent hurricanes, floods, heat waves, and droughts, and leads to sea level rise and coastal erosion as a result of ocean warming, melting of glaciers, ad loss of ice sheets.

The climate crisis refers to the serious problems that are being caused, or are likely to be caused, by changes in the planet’s climate, including weather extremes and hazards, ocean acidification and sea-level rise, loss of biodiversity, food and water insecurity, health risks, economic disruption, displacement, and even violent conflict.

Since the 1800s, human activities have caused the Earth’s average temperature to increase by about 1.2° C – with more than two-thirds of this warming occurring since 1975. This is already causing significant damage to human societies and natural ecosystems in many parts of the world. More than 3 billion people live in places that are very vulnerable to the climate crisis, with lower income countries being disproportionately affected.

Scientists expect that an increase beyond 1.5°C would begin to lead to a series of dangerous tipping points that would make many changes irreversible and pose a very serious threat to human civilization. This is why governments must act now to drastically reduce greenhouse gas emissions and chart a course for reaching net zero in the coming decades, invest in adaptation to the unavoidable impacts of climate change, and protect and restore natural ecosystems and biomes upon which the planet depends.

Climate feedback loops happen when one change in the climate triggers further changes, in a chain reaction that reinforces itself as time goes on. Ultimately, feedback loops can trigger tipping points, at which point the changes to our planet’s climate systems become severe and irreversible.

Currently, scientists are aware of some serious feedback loops that are driving global warming. For example, as sea ice in the Arctic melts, more heat is being absorbed by the darker ocean waters, thus speeding up the warming process and leading to more ice melting. Similarly, as wildfires burn down forests, they release greenhouse gases leading to more warming and more wildfires. Other feedback loops include the thawing of the permafrost, forest dieback, and insect outbreaks.

A tipping point is a threshold after which certain changes caused by global warming and climate change become irreversible, even if future interventions are successful in driving down average global temperatures. These changes may lead to abrupt and dangerous impacts with very serious implications for the future of humanity and our planet.

As the world gets hotter, several tipping points are becoming very likely. One of them is the collapse of the Greenland and West Antarctic ice sheets, which would lead to significant sea level rise and threaten coastal communities and ecosystems. Another is the thawing of the permafrost in the tundra regions, which will release huge quantities of trapped greenhouse gases, further accelerating global warming and climate change. Mass coral bleaching events and the destruction of rainforests are two other major tipping points with immense implications for both biodiversity and human societies.

Under the Paris Agreement, countries are expected to take the necessary measures to avoid dangerous climate change by limiting global warming to well below 2°C, and pursuing efforts to limit it to 1.5°C. But even best-case scenarios now indicate a significant chance of overshooting these goals, even if temporarily. Climate overshoot refers to the period during which warming will have increased past 1.5° C, before falling back down. This period will probably occur around the middle of this century, but troubling signs are emerging that it may occur even earlier.

The longer the climate overshoot lasts, the more dangerous the world will become. A prolonged period of higher global temperatures will have devastating and irreversible impacts on natural ecosystems, biodiversity, and human communities, particularly in dry areas, coastal zones, and other vulnerable locations. Making deep emission cuts during this decade is of extreme importance to limiting the duration and impacts of the climate overshoot.

Climate change mitigation refers to any action taken by governments, businesses, or people to reduce or prevent greenhouse gas emissions, or to enhance carbon sinks that remove these gases from the atmosphere.

Reducing or preventing greenhouse gas emissions can be achieved by transitioning to renewable energy sources like wind and solar, using energy more efficiently, adopting low carbon or carbon-free transportation modalities, promoting sustainable agriculture and land use, and changing production and consumption models and diet behaviours. Enhancing carbon sinks can be achieved by restoring forests, wetlands, and marshlands, maintaining soil health, and protecting terrestrial and marine ecosystems.

In order for mitigation actions to be successful, it is crucial that countries develop supportive environments through legislation, policies, and investments.

Did you know: To limit global warming to 1.5° C, which is the critical goal of the Paris Agreement, the world must implement climate change mitigation actions to reduce greenhouse gas emissions by 45 percent before 2030 and reach net-zero by mid-century.

Climate change adaptation refers to actions that help reduce vulnerability to the current or expected impacts of climate change like weather extremes and hazards, sea-level rise, biodiversity loss, or food and water insecurity.

Even in very positive scenarios in which we manage to significantly and swiftly cut greenhouse gas emissions, climate change will continue to impact our world for decades to come because of the energy already trapped in the system. This means widespread adaptation is needed to limit these impacts and safeguard people and nature.

Many adaptation measures need to happen at the local level, so rural communities and cities have a big role to play. Such measures include planting crop varieties that are more resistant to drought and practicing regenerative agriculture, improving water storage and use, managing land to reduce wildfire risks, and building stronger defenses against extreme weather like floods and heat waves.

However, adaptation also needs to be driven at the national and international levels. In addition to developing the policies needed to guide adaptation, governments need to look at large-scale measures such as strengthening or relocating infrastructure from coastal areas affected by sea-level rise, building infrastructure able to withstand more extreme weather conditions, enhancing early warning systems and access to disaster information, developing insurance mechanisms specific to climate-related threats, and creating new protections for wildlife and natural ecosystems.

Climate resilience is the capacity of a community or environment to anticipate and manage climate impacts, minimize their damage, and recover and transform as needed after the initial shock.

To best safeguard societal wellbeing, economic activity, and the environment, people, communities, and governments need to be equipped to deal with the unavoidable impacts of climate change. This can be done by training people to obtain new skills and diversify the sources of their household income, building more robust disaster response and recovery capacities, enhancing climate information and early warning systems, and working on long-term planning, among others.

Ultimately, a truly climate-resilient society is a low-carbon one, because drastically reducing greenhouse gas emissions is the best way to limit how severe climate impacts will be in the future. It is also a society based in equity and climate justice that prioritizes support for people and communities most exposed to climate impacts or least able to cope with them.

A carbon footprint is a measure of the greenhouse gas emissions released into the atmosphere by a particular person, organization, product, or activity. A bigger carbon footprint means more emissions of carbon dioxide and methane, and therefore a bigger contribution to the climate crisis.

Measuring a person’s or an organization’s carbon footprint entails looking at both the direct emissions resulting from the burning of fossil fuels for energy production, heating, and land and air travel, and indirect emissions resulting from the production and disposal of all food, manufactured goods, and services they consume.

Carbon footprints can be reduced by shifting to low-carbon energy sources like wind and solar, improving energy efficiency, strengthening industry policies and regulations, changing purchasing and travel habits, and reducing meat consumption and food waste.

Climate justice means putting equity and human rights at the core of decision-making and action on climate change.

One aspect of climate justice relates to the unequal historical responsibility that countries bear in relation to the climate crisis. The concept suggests that the countries, industries, and businesses that have become wealthy from activities that emitted the most greenhouse gas emissions have a responsibility to help mitigate the impacts of climate change on those affected, particularly the most vulnerable countries and communities, who often are the ones that have contributed the least to the crisis.

Even within the same country, because of structural inequalities based on race, ethnicity, gender, and socioeconomic status, the responsibilities in addressing climate change need to be divided fairly, with the biggest responsibility resting on those who have contributed to, and benefitted from, causing the crisis the most.

Another aspect of climate justice is the intergenerational one. Children and young people today have not contributed to the climate crisis in a significant way but will bear the full force of climate change impacts as they advance through life. Because their human rights are threatened by the decisions of previous generations, they must have a central role in all climate decision-making and action.

Nature-based solutions are actions to protect, conserve, restore, and sustainably use and manage ecosystems to support climate change adaptation and mitigation efforts, preserve biodiversity, and enable sustainable livelihoods. They are actions that prioritize the importance of ecosystems and biodiversity and are designed and implemented with the full engagement and consent of local communities and Indigenous Peoples, who hold generational knowledge on protecting nature.

Nature-based solutions are used in many ways, across terrestrial, freshwater, coastal, and marine ecosystems. Restoring wetlands protects communities from floods, while conserving mangrove forests supports food sources and minimizes the impact of storms. Forests absorb carbon dioxide, allow biodiversity to thrive, increase water security, and combat landslides, while urban parks and gardens help cool down cities and limit the impact of heatwaves. Regenerative agriculture practices increase the amount of carbon captured by the soil and restore its health and productivity.

Nature-based solutions are seen as a win-win for people and nature, addressing multiple problems at once. They can create jobs, provide new and more resilient livelihood opportunities, and increase income while also protecting the planet and addressing climate change.

Indigenous Peoples’ ways of life are inherently low-carbon and emphasize balance between humans and the natural world. Their traditional practices have low impact on the environment and are responsive to it, fostering self-sustaining ecosystems.

Indigenous Peoples were among the first to notice climate change and their knowledge and practices help navigate and adapt to its impacts. Indigenous knowledge, which is intergenerational and community-based, is a great source of meaningful climate solutions that can advance mitigation, enhance adaptation, and build resilience. It can also complement scientific data with precise landscape information that is critical to evaluating climate change scenarios.

Indigenous Peoples protect an estimated 80 percent of the world’s remaining biodiversity yet continue to be largely excluded from almost all global decision-making processes on climate change. Their collective knowledge, valuable insights, and rights to their ancestral lands, territories and resources, and their way of life must be recognized and included across climate policies and actions.

There is no agreed definition of "Loss and damage" in the international climate negotiations. However, the term can refer to the unavoidable impacts of climate change that occur despite, or in the absence of, mitigation and adaptation. Importantly, it highlights that there are limits to what adaptation can accomplish; when tipping point thresholds are crossed, climate change impacts can become unavoidable.

Loss and damage can refer to both economic and non-economic losses. Economic loss and damage can include things like the costs of rebuilding infrastructure that has repeatedly been damaged due to cyclones or floods, or the loss of coastline land (and homes and businesses) due to sea-level rise and coastal erosion.

Non-economic loss and damage include negative impacts that can’t be easily assigned a monetary value. This can include things such as trauma from experiencing weather extremes and hazards, loss of life, the displacement of communities, loss of history and culture or loss of biodiversity.

Climate change can exacerbate food, water, and livelihood insecurity, with cascading effects such as displacement and migration and increased competition over natural resources, all of which can lead to increased tensions and instability in a country or a region. Furthermore, the impacts of climate change can aggravate or prolong existing violent conflicts and make it more difficult to deliver climate action and to reach and sustain peace. 

Climate security refers to evaluating, managing, and reducing the risks to peace and stability brought on by the climate crisis. This means ensuring that climate mitigation and adaptation goes beyond doing no harm and contributes positively to peace and stability. It also means that conflict prevention and peacebuilding interventions take climate impacts into account. The technical solutions to climate action and adaptation can serve as opportunities to build peace and mend the social fabric, especially in countries affected by conflict and fragility.

Did you know: Climate action can help alleviate the underlying drivers of conflict and fragility. For example, access to renewable energy can be a lifeline which supports clean water, light, warmth, and sustenance, as well as basic and emergency services. It also powers local economic development, while setting countries on a sustainable development pathway to recovery.

Climate finance refers to financial resources and instruments that are used to support action on climate change. Climate finance is critical to addressing climate change because of the large-scale investments that are needed to transition to a low-carbon global economy and to help societies build resilience and adapt to the impacts of climate change.

Climate finance can come from different sources, public or private, national or international, bilateral or multilateral. It can employ different instruments such as grants and donations, green bonds, debt swaps, guarantees, and concessional loans. And it can be used for different activities, including mitigation, adaptation, and resilience-building.

Some multilateral funds that countries can access include the Green Climate Fund (GCF), the Global Environment Facility (GEF), and the Adaptation Fund (AF). High-income countries with a significant historical contribution to climate change have committed to raising US$100 billion every year to fund climate action in low-income countries. However, this target has not yet been reached and more funding is required for both mitigation and adaptation interventions.

Did you know: Many studies and reports show that investments in climate action can yield results that dramatically outweigh the upfront costs. One study by the World Bank shows that an investment of US$1 can yield, on average, $4 in benefits.

Reaching net zero requires us to ensure that carbon dioxide emissions from human activity are balanced by human efforts to remove carbon dioxide emissions (for example, by creating carbon sinks to absorb carbon dioxide) - thereby stopping further increases in the concentration of greenhouse gases in the atmosphere. 

Transitioning to net zero requires a complete transformation of our energy, transportation, and production and consumption systems. This is necessary to avert the worst consequences of climate change.

Did you know: To keep global warming below 1.5°C, the world’s governments need to ensure that all greenhouse gas emissions peak by 2025, and reach net zero in the second half of this century. The IPCC has recommended to reduce CO2 emissions globally by 45% before 2030 (compared to 2010 levels) and reach net zero by mid-century.

Decarbonization means reducing the amount of greenhouse gas emissions that a society produces, as well as increasing the amount that is being absorbed. It entails changing many, if not all, aspects of the economy, from how energy is generated, to how goods and services are produced and delivered, to how buildings are built and how lands are managed.

To meet the goals of the Paris Agreement and keep the 1.5° target alive, governments and businesses must rapidly decarbonize by 2030. Meaningful decarbonization requires substantial investments in low-carbon infrastructure and transportation, renewable energy sources, circular economy and resource efficiency, and land and soil restoration. It also requires a rethinking of current economic models that are focused on growth at all costs.

Renewable energy is energy derived from natural sources that are constantly being replenished, such as wind, sunlight, the flow of moving water, and geothermal heat. In contrast to energy sourced from fossil fuels like coal, oil, and gas, which accounts for 75 percent of the harmful greenhouse gas emissions that are causing climate change, energy from renewable sources is cheap, clean, sustainable, and generates more jobs.

Transitioning from fossil fuels to renewable energy in all sectors – power, heating and cooling, transportation, and industry – is key to addressing the climate crisis. To stay under 1.5°C of global warming, the world needs to immediately phase out fossil fuel use and undergo a profound transformation of the energy system through rapid electrification and sourcing energy from renewable sources.

Did you know: In 2022, renewable sources provided 29 percent of global electricity. With the right investments, electricity from renewable sources could provide 65 percent of the world’s total electricity supply by 2030.

A carbon sink is any process, activity, or mechanism that absorbs more carbon dioxide from the atmosphere than it releases. Forests, oceans, and soil are the world’s largest natural carbon sinks.

Oceans absorb carbon dioxide from the atmosphere through marine ecosystems and the plant and animal life they harbor. Sequestering carbon in marine ecosystems is generally referred to as blue carbon. Forests and soil are the other main natural carbon sinks of the planet, storing carbon in trees and vegetation, wetlands and peat bogs, and plant litter.

Today, human activity, like burning fossil fuels and deforestation, causes more carbon to be released into the atmosphere than the Earth’s natural carbon sinks can absorb, leading to global warming and climate change. Human activities and climate change are also causing the degradation of these natural carbon sinks, threatening the release of the carbon they store back into the atmosphere. Therefore, protecting carbon sinks and expanding their capability to absorb carbon and store it long-term is a key strategy for tackling climate change and stabilizing the climate.

Carbon removal is the process of removing greenhouse gas emissions from the atmosphere, through natural solutions such as reforestation and soil management or technological solutions like direct air capture and enhanced mineralization. Carbon removal is not a substitute for cutting greenhouse gas emissions, but it can slow down climate change and is necessary to shorten any period during which we temporarily overshoot our climate targets.

Carbon capture and storage is the process of trapping carbon emissions produced by fossil fuel power plants or other industrial processes before they can enter our atmosphere by storing them deep underground. Carbon capture and storage should not be seen as an alternative to the green energy transition, but it has been proposed as a way to tackle emissions from sectors that are difficult to decarbonize, particularly heavy industries like cement, steel, and chemicals.

However, these technologies are only in the early development stage and will require carefully-designed policies. Dramatically slashing greenhouse gas emissions must remain the top priority to combat the climate crisis.

Carbon markets are trading schemes that create financial incentives for activities that reduce or remove greenhouse gas emissions. In these schemes, emissions are quantified into carbon credits that can be bought and sold. One tradable carbon credit equals one tonne of carbon dioxide, or the equivalent amount of a different greenhouse gas reduced, sequestered or avoided.

Carbon credits can be bought by countries as part of their NDC strategy, by corporations with sustainability targets, and by private individuals that want to compensate for their carbon footprint.

The supply of carbon credits comes from private entities or governments that develop programmes to reduce or remove emissions. These programmes are certified by a third party and registered under a carbon market standard.

For carbon markets to be successful, countries must work together to secure robust carbon accounting, ensure transparency for carbon market transactions, implement safeguards against human rights abuses and other adverse societal impacts, and combat greenwashing and the misrepresentation of carbon-neutral products and services.

Regenerative agriculture is a way of farming that nurtures and restores soil health, and therefore reduces water use, prevents land degradation, and promotes biodiversity. By minimizing land ploughing, practicing rotating crops, and using animal manure and compost, regenerative agriculture ensures that the soil stores more carbon, conserves more moisture, and is healthier due to thriving fungal communities.

Intensive agriculture is responsible for a third of global greenhouse gas emissions, uses 70 percent of the fresh water we consume, and leads to soil degradation through its use of heavy machinery, chemical fertilizers, and pesticides. It is also the biggest contributor to biodiversity loss. By contrast, regenerative agriculture helps lower greenhouse gas emissions, conserves water, and restores land. Moreover, healthy soil produces more food and better nutrition and has other positive impacts on ecosystems and biodiversity.

Forests provide immense benefits by removing carbon dioxide and pollutants from the atmosphere, preventing soil erosion, filtering water, and housing half of the world’s land species of animals, plants and insects. Reforestation and afforestation are two of the most effective nature-based solutions in fighting climate change and limiting its impacts.

Reforestation is the process of replanting trees in areas that had recent tree cover but where forests were lost, due to wildfires, drought, disease, or human activity such as agricultural clearing.

Afforestation is the process of planting trees in areas that have not been forested in recent history. Afforestation helps restore abandoned and degraded agricultural lands, prevent desertification, create carbon sinks, and generate new economic opportunities for local communities.

Rewilding is the mass restoration of ecosystems that have been damaged by human activity. More than conservation, which focuses on saving specific species through dedicated human intervention, rewilding refers to setting aside large areas for the natural world to regenerate in on its own terms. This sometimes requires the reintroduction of key species that have been driven extinct in a particular region, such as beavers, wolves, or large herbivores, who help shape entire ecosystems.

Rewilding can help combat climate change by removing more carbon dioxide from the atmosphere through healthy natural processes such as natural woodland regeneration. It also helps prevent species extinction by creating nature-rich habitats that allow wildlife to adapt to climate change and migrate as warming intensifies.

Circular economy refers to models of production and consumption that minimize waste and reduce pollution, promote sustainable uses of natural resources, and help regenerate nature.

Circular economy approaches are all around us. They can be employed in a number of different sectors from textiles to buildings and construction, and at various stages of a product’s lifecycle, including design, manufacturing, distribution, and disposal.

Besides helping tackle the problem of pollution, circular economy approaches can play a critical role in solving other complex challenges such as climate change and biodiversity loss. They can help countries accelerate their transition to more resilient and lower-carbon economies while also creating new green jobs.

Did you know: Currently, only 7.2 percent of used materials are cycled back into our economies after use. This has a significant burden on the environment and contributes to the climate, biodiversity, and pollution crises. As a result, we currently need about 1.7 Earths to deliver on all the world's resource demands.

The world’s oceans – their temperature, chemistry, currents, and life – drive global systems that make Earth habitable for humankind. Our rainwater, drinking water, weather, climate, coastlines, much of our food, medicines and even the oxygen in the air we breathe, are all provided and regulated by the seas. However, because of climate change, the health of our oceans is now at significant risk.

The "blue economy" concept seeks to promote economic development, social inclusion, and the preservation or improvement of livelihoods while at the same time ensuring environmental sustainability of the oceans and coastal areas.

Blue economy has diverse components, including established traditional ocean industries such as fisheries, tourism, and maritime transport, but also new and emerging activities, such as offshore renewable energy, aquaculture, seabed extractive activities, and marine biotechnology.

Green jobs are decent jobs that contribute to protecting and restoring the environment and addressing climate change. Green jobs can be found in both the production of green products and services, such as renewable energy, and in environmentally friendly processes, such as recycling. Green jobs help improve energy and raw material efficiency, limit greenhouse gas emissions, minimize waste and pollution, protect and restore ecosystems, and support adaptation to the impacts of climate change.

As the market for green jobs is expanding, countries must ensure that the workforce is equipped with the specific skills and education required to carry them out. This can be achieved by investing in training young people for future green jobs and by retraining workers from carbon-intensive industries. The latter is a key part of ensuring countries are pursuing a just transition and leave no one behind.

With public pressure to address the climate crisis rising, private sector companies are joining the transition to a low-carbon global economy. However, their efforts can sometimes turn into more of a marketing exercise than real, meaningful action.

Greenwashing refers to situations where a company makes misleading claims about their positive environmental impact or the sustainability of their products and services to convince consumers that they are acting on climate change. In some cases, greenwashing can be unintentional, because of lack of knowledge on environmental issues. However, it can also be carried out intentionally as a marketing and public relations exercise, exploiting public support towards environmental policies for profit.

Greenwashing can erode public confidence in sustainability and allow negative environmental impacts to continue unabated.

In the context of climate change, transitioning to a low-carbon or net-zero economy requires massive transformation of our economic systems. Such transformation runs the risk of further increasing social inequality, exclusion, civil unrest, and less competitive businesses, sectors, and markets.

As countries work to meet their climate goals, it’s vital that they ensure the whole-of-society – all communities, all workers, all social groups – are brought along and part of the structural change that takes place.

Ensuring a just transition means that countries choose to green their economy through transition pathways and approaches that reinforce equality and inclusivity. This means looking at the impacts of the transition on different groups of workers across the economy and providing opportunities for training and reskilling that support decent work and aim to leave no one behind.

The United Nations Framework Convention on Climate Change (UNFCCC) is an international environmental treaty adopted in 1992 to combat dangerous human interference with the climate system. It entered into force in 1994 and enjoys near universal membership, having been signed by 198 parties. It is the parent treaty of both the Paris Agreement and the Kyoto Protocol.

The UNFCCC secretariat is the United Nations entity tasked with supporting the global response to the threat of climate change. The secretariat facilitates intergovernmental climate change negotiations by organizing between two and four negotiating sessions each year, the largest and most important of which is the Conference of the Parties (COP). It also provides technical expertise and assists in the analysis and review of climate change information and maintains the registry of Nationally Determined Contributions (NDC).

The annual United Nations conference dedicated to climate change, called the “Conference of the Parties” or “COP,” has been organized under the UN Framework Convention on Climate Change (UNFCCC) since 1995. At the 21st COP, or COP21, which took place in 2015, the Paris Agreement was signed.

The conference now brings together all nations who are parties to the Paris Agreement to discuss their next steps to combat climate change and further establish legally binding agreements to support climate action.

The Paris Agreement is a legally binding international treaty aiming to limit global warming to well below 2° C, preferably to 1.5° C, compared to pre-industrial levels. It was adopted by 196 Parties in 2015 at COP21 in Paris and entered into force in 2016.

The Paris Agreement is a landmark achievement in international cooperation on climate change because it is a binding agreement for all Parties to scale up efforts to combat climate change and adapt to its effects. It also provides the instruments for developed nations to assist developing nations in their climate mitigation and adaptation efforts, while creating a framework for transparent monitoring and reporting of results.

Nationally Determined Contributions (NDCs) are climate pledges and action plans that each country is required to develop in line with the Paris Agreement goal of limiting global warming to 1.5° C. NDCs represent short to medium-term plans that are updated every five years with higher ambition on climate.

NDCs outline mitigation and adaptation priorities a country will pursue to reduce greenhouse gas emissions, build resilience, and adapt to climate change, as well as financing strategies and monitoring and verification approaches. In 2023, the first in a series of global “stock takes” will conclude that assesses progress on the implementation of NDCs and Paris Agreement goals.

Under the Paris Agreement, countries must regularly report on the implementation of their Nationally Determined Contributions. It is crucial that this reporting is done with transparency to allow the global community to accurately assess collective progress and build trust that everyone is playing their part.

Transparent reporting allows governments and international bodies to have access to reliable data and make evidence-based decisions. It also enhances our scientific understanding of climate change and the actions and policies needed to mitigate it and adapt to its impacts. Ultimately, transparency is key to unlocking the full potential of the Paris Agreement, by promoting trust, collaboration and knowledge transfer and encouraging further ambition on climate targets.

National Adaptation Plans (NAPs) help countries plan and implement actions to reduce vulnerability to the impacts of climate change and strengthen adaptive capacity and resilience. NAPs link to Nationally Determined Contributions (NDCs) and other national and sectoral policies and programmes.

For NAPs to be successful they need to be participatory, inclusive, gender-responsive, and transparent. This means that at the design stage, NAPs need to evaluate the specific needs and vulnerabilities of different groups in the country, paying particular attention to those most vulnerable to climate change impacts and involving them in developing and implementing strategies and programmes.

Under the Paris Agreement, countries are invited to communicate long-term strategies (LTS) for emissions reductions that envision a whole-of-society transformation over several decades, usually up to 2050. LTS documents align to the long-term objectives of limiting global warming and achieving net-zero by 2050.

Long-term strategies provide a long-term vision that gives coherence and direction to shorter-term national climate pledges like the NDCs. They guide countries to pursue low-carbon development and prevent fossil fuel-intensive investments, demonstrating the socio-economic benefits of the green transition. They boost innovation and can help drive investment in low-carbon solutions and sustainable infrastructure. And they help facilitate and promote just and equitable transitions for the people who are most affected, making sure that climate solutions are fair and inclusive.

When countries officially communicate their LTS to the UNFCCC it is called a Long-Term Low Emission Development Strategy (LT-LEDS). All submissions can be accessed on the UNFCCC website.

Forest conservation and restoration can provide more than one quarter of the greenhouse gas emissions reductions needed to avoid the worst impacts of climate change. REDD+ is a framework agreed by countries in the international climate negotiations that aims to curb climate change by reducing deforestation and forest degradation, and sustainably managing and conserving forests in developing countries.

REDD stands for "Reducing Emissions from Deforestation and forest Degradation”. The “+” signifies the role of conservation, sustainable management of forests and enhancement of forest carbon stocks.

The Intergovernmental Panel on Climate Change (IPCC) is an independent body founded under the auspices of the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP).

The IPCC’s main role is to assess the scientific literature and findings on climate change and provide vital scientific information and evidenced-based recommendations to policymakers and the public. It is widely recognized as the most credible source of information related to the science of climate change and its complex analysis of impacts, risks, and adaptation and mitigation options.

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Climate Glossary

Climate Glossary