An A-Z glossary of climate change terms and definitions

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Knowledge is a tool for empowerment. Climate Action depends on an awareness of accurate information, considered decision-making, and effective leadership. But the terms, definitions, and acronyms used in climate change discourse can prove a little confusing.

 

Do you know the difference between global warming and global heating, for example? How does afforestation relate to deforestation and reforestation? How does Annex I Parties differ from Annex II Parties? You’ve likely heard of the abbreviation CO2, but what does CH4 mean and why is it so important?

 

If you’re struggling, worry not. Below we present our glossary, complete with all the essential climate terms and with the express aim of simplifying them as much as possible, transforming climate jargon into simple English.

 

Skip to relevant letter:

 

A – B – C – D – E – F – G – H – I – J – K – L – M – N – O – P – Q – R – S – T – U – V – W – X – Y – Z

 

 

A

 

Adaptation: The act of adjusting natural or human systems to the shifting environment, with the goal of moderating harm to the climate or taking advantage of beneficial opportunities.

 

Adaptive capacity: A measurement of our adaptation capabilities.

 

Aerosols: Small particles or liquid droplets that absorb or reflect sunlight.

 

Afforestation: The act of planting new trees and new forests. The opposite process of deforestation.

 

Alternative energy: Refers to energy sources that stems from non-traditional places, with examples including compressed natural gas, solar, hydroelectric, and so on.

 

Annex I Parties: Countries included in the Annex I to the UN Framework Convention on climate change, which involved all the developed countries in the Organisation for Economic Co-operation and Development (OECD), and economies in transition.

 

Annex II Parties: The countries listed in Annex II to the Convention that have a special obligation to provide financial resources and facilitate technology transfer to developing countries. Annex II Parties include the 24 original OECD members plus the European Union.

 

Anthropocene: Term that describes the period of time during which human activities have impacted the environment enough to constitute a distinct geological change.

 

Anthropogenic: Term used to describe phenomena created by human activity.

 

Anthropogenic removals: Refers to attempts to remove greenhouse gases from the atmosphere through human activity. These include enhancing biological sinks of CO2, chemical engineering, carbon capture and storage, and so on.

 

Atmosphere: A layer of gas, or layers of gases, that surround a planet. The Earth’s atmosphere is mostly made up of Nitrogen (approximately 78%) and oxygen (approximately 21%) along with small trace gases and active greenhouse gases, such as CO2 (approximately 0.035% of mixing ratio).

 

 

B

 

Baseline scenario: Scenarios that assume no changes will be implemented further than those in force.

 

Biodiversity: Explains the variability among living organisms from all sources: animals, plants, fungi, micro-organisms, and so on. All work together in ecosystems to build, balance, and support life.

 

Biofuels: Fuel made from plant material. Includes wood, peat, agricultural waste, fires, waste alcohol, and so on. Biofuels generally produce fewer emissions than fossil fuels. Also known as bioenergy.

 

Biosphere: Part of the Earth system comprising all ecosystems and living organisms, including in the atmosphere (see above), on land (terrestrial biosphere), or in the oceans (marine biosphere).

 

Burden sharing: In terms of mitigation, refers to sharing efforts and reducing sources of emissions from historical or projected levels, as well as sharing the burden to countries across the world. It is an important term, particularly when considering responsibilities for emissions between countries.

 

 

C

 

Carbon budget: The maximum amount of cumulative net global anthropogenic CO2 emissions that would result in limiting global warming to a given level with a given probability.

 

Carbon dioxide (CO2): A naturally occurring gas and a by-product of burning fossil fuels and biomass. It is the principal human-caused greenhouse gas that affects the Earth’s radiative balance.

 

Carbon capture: Any form of tech that reduces CO2 emissions.

 

CO2 equivalent: Metric that helps compare emissions of other greenhouse gases to CO2, which broadly makes it easier to track and measure the impact of other greenhouse gases.

 

CO2 fertilisation: Growth of plants as a result of increased CO2 concentration.

 

Carbon footprint: The total amount of greenhouse gases emitted by individuals per year, or by organisations, buildings, teams, and so on.

 

Carbon leakage: Refers to situations in which industry relocates to countries where emission regimes are weaker, or non-existent.

 

Carbon offsetting: Term refers to the act of compensating for CO2 emissions. Offsetting usually involves paying another party and contributing to saving equivalent emissions to your activity, most commonly known when individuals travel by plane.

 

CH4: Refers to methane, a potent greenhouse gas that is more powerful than CO2 and responsible for 30% of the rise in temperatures since the industrial revolution. The largest source of methane is animal agriculture and food production, hence recent calls for the adoption of plant-based diets.

 

Chlorofluorocarbons (CFCs): Gases typically used for refrigeration, air conditioning, packaging, insulation, solvents, or aerosol propellants. CFCs often break down ozone, and the ozone layer.

 

Climate: The average weather, in the simplest terms. But more strictly refers to mean and variability of relevant quantities over time, such as temperature, precipitation, wind, and so on.

 

Climate change: Refers to significant changes to the climate, as defined above.

 

Climate model: A quantitative way of representing interactions with climate, ranging from simple models to complex ones. Helps to establish future projections and enhance decision-making abilities.

 

Climate system: Refers to the five physical components responsible for the climate: atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere.

 

Conference of Parties (COP): COP is the name given to the United Nations Climate Change Conferences. The goal of these conferences is to review progress made by members of the United Nations Framework Convention on Climate Change (UNFCCC) to limit climate change.

 

Concentration: Amount of a chemical in a volume or weight of air, water, soil, or other medium. Vital in terms of tracking the concentration of CO2 (and other gases) in the atmosphere.

 

Coral bleaching: Due to environmental stress, coral colonies remove a microscopic algae called zooxanthellae, which makes the corals appear whitened.

 

Corporate Social Responsibility (CSR): By practicing corporate social responsibility, companies can be conscious of the kind of impact they are having on all aspects of society, including economic, social, and environmental impacts.

 

Cryosphere: Part of the climate system. The cryosphere is frozen water in the form of snow, permafrost, floating ice, and glaciers. Fluctuations of the cryosphere cause changes in ocean sea level.

 

 

D

 

Decoupling: A scenario in which economic growth no longer depends on the consumption of fossil fuels. Often split into relative and absolute decoupling.

 

Deforestation: The destruction of forested land. Contributes to increases in CO2 through burning of wood that release CO2 and the removal of trees that take CO2 from the atmosphere.

 

Desertification: The process by which land becomes arid, semi-arid, or dry due to factors relating to climactic variations caused by human activity.

 

Drought: Abnormally dry weather that lasts long enough to cause hydrological imbalance.

 

 

E

 

Ecosystem: Natural unit or natural entity that includes living and non-living parts that interact to produce a stable system through cyclic exchange of materials.

 

El Niño: El Niño is a climate pattern describing unusual warming of surface waters in the eastern tropical Pacific Ocean. El Niño is the warm phase of the El Niño-Southern Oscillation.

 

Emissions: Substance released into the atmosphere, usually referring to greenhouse gases.

 

Energy efficient: Often used to label products or services that use less energy than competitors.

 

Enteric fermentation: The process by which livestock, especially cattle, produce methane as part of their digestion. The process roughly represents one third of emissions from the agricultural sector. And food systems account for over one-third of global greenhouse gas emissions.

 

Environmental, social, and governance (ESG): Criteria that screen company policies and encourage companies to act ethically. Examines how companies manage relationships with employees, suppliers, customers, communities, and so on. Increasingly important for investors.

 

 

F

 

Feedback loop: Refers to the way in which temperatures change the environment, which causes further changes to the environment. Feedback loops can be positive (adding to warming), or negative (reducing warming), and various examples exist in the current climate system.

 

Fluorinated gases: Synthetic greenhouse gases such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, all emitted from industrial processes.

 

Fossil fuels: Refers to organic materials that are made from decaying plants and animals that can be converted through human activity into crude oil, coal, natural gas, or heavy oils.

 

Fuel switching: The act of substituting one type of fuel for another, often in relation to finding alternatives that emit fewer emissions and prove more environmentally-friendly.

 

 

G

 

Geosphere: Refers to soil, sediments, and rock layers of the Earth’s crust.

 

Geoengineering: The deliberate large-scale intervention in the Earth’s natural systems to attempt to counteract climate change. Carbon capture is an example of geoengineering.

 

Glacier: Refers to a mass of ice at least 0.1 km2 that shows evidence of movement. The glacier is usually caused by the accumulation of snowfall over many years. Glacier ice is the largest reservoir of fresh water on Earth and thus important in the fight against global warming.

 

Global warming: Refers to average increases in temperature near the surface of the Earth, caused by greenhouse emissions blanketing the Earth and trapping the sun’s heat.

 

Greenhouse effect: Refers to the trapping of heat in the atmosphere. Some of the heat flowing back from the Earth’s surface is absorbed by greenhouse gases – the most prominent gases in the atmosphere, such as oxygen and nitrogen, cannot absorb any heat.

 

Greenhouse gas: Greenhouse gases absorb infrared radiation in the atmosphere, trapping heat and leading to a warming climate. There are many greenhouse gases: CO2, CH4, nitrous oxide, ozone, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, and so on.

 

Greenwashing: The act of making it seem like you are participating in and profiting from activities that are environmentally friendly without taking meaningful action on climate change.

 

 

H

 

Heat waves: Prolonged periods of excessive heat, usually combined with excessive humidity.

 

Hydrocarbons: Refers to substances that contain only hydrogen and carbon – fossil fuels are made up of hydrocarbons, for example.

 

Hydrologic cycle: 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.

 

Hydrosphere: Part of the climate system. The hydrosphere comprises of liquid surface and water, including oceans, seas, rivers, lakes, underground water, and so on.

 

 

I

 

Indirect emissions: Greenhouse gas emissions from a building or a home that occur as a result of electricity used in that building.

 

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. The period marks the beginning in the general dependence on fossil fuels – and thus the growth of CO2 emissions.

 

The Intergovernmental Panel on Climate Change (IPCC): The IPCC is a scientific body established by the UN Environment Programme and the World Meteorological Organization. The role of the IPCC is to review and assess scientific, technical, and socio-economic work relevant to climate change. The IPCC is a great resource for people tracking and measuring the current rate of climate change.

 

 

J

 

Climate justice: Refers to justice that links human rights and development while simultaneously addressing climate change. Often aims to safeguard rights of the vulnerable and share the burden of climate change to ensure fair, just, and equitable outcomes.

 

 

K

 

Kyoto Protocol: An international treaty adopted in December 1997 in Kyoto, Japan. The Kyoto Protocol has many binding commitments, with counties agreeing to reduce greenhouse gas emissions by at least 5% below 1990 levels between 2008–2012. Many of the goals and commitments established in Kyoto have not been realised.

 

 

L

 

Life cycle assessment: The evaluation of the inputs and outputs of a product or service throughout its life cycle, broadly showing potential environmental impacts.

 

Longwave radiation: Radiation emitted in the spectral wavelength that is greater than four micrometers, corresponding to the radiation emitted from the Earth and atmosphere.

 

 

M

 

Megacities: Refers to any city that has a population of more than ten million people.  

 

Megadams: Although there is no universal definition, megadams usually refer to large structures more than 15 metres in height that generate more than 400 megawatts of power on average. They have proved controversial around ideas of displacement and inequality.

 

Methane: Hydrocarbon greenhouse gas with a global warming potential most recently estimated at 25 times that of CO2, although other estimates rank methane as far more potent. See CH4.

 

Migrant: The International Organisation for Migration defines a migrant as a ‘person who is moving or has moved across an international border or within a State away from habitual place of residence’. Projections suggest that climate change will lead to a massive increase in migrants across the world.

 

Mitigation: Human intervention to reduce the impact on the climate system. Mitigation can refer to any strategy that reduces emissions, or enhances sinks, or broadly engages in climate action.

 

 

N

 

Natural gas: Underground deposits of gases that consist of 50–90% CH4, along with small amounts of hydrocarbon compounds such as propane (C3H8) and butane (C4H10).

 

Negative emissions: The removal of greenhouse gases from the atmosphere by human activities.

Net zero: Simply means cutting greenhouse gas emissions to zero. Could be achieved by limiting anthropogenic emissions, or engaging in anthropogenic removals of emissions.

 

Nitrogen oxides (NOx): Gases produced by vehicle exhausts and power stations. Can contribute to photochemical ozone (otherwise known as smog), impair visibility, and have health consequences.

 

Nitrous oxide (N2O): Greenhouse gas with warming potential of roughly 300 times CO2. Fertilisers, fossil fuel combustion, nitric acid production, and biomass burning all emit N20.

 

 

O

 

Ocean acidification: Increased concentrations of CO2 in sea water that causes increases a reduction in ocean PH and could damage marine ecosystems.

 

Ocean fertilisation: Increasing nutrients to oceans to enhance biological production. The process may lead to increased sequestering of CO2 from the atmosphere.

 

Ozone (troposphere): Ozone a gaseous atmospheric constituent, created by natural sources and human activities through photochemical smog. In high concentrations, tropospheric ozone can harm a wide range of organisms and can act as a greenhouse gas.

 

Ozone (stratosphere): Ozone in the stratosphere plays a role in radiative balance. Depletion of ozone, due to chemical reactions climate change may enhance, results in increased ultraviolent radiation.

 

Ozone depleting substance: Refers to man-made compounds, including chlorofluorocarbons, hydrochlorofluorocarbons, bromofluorocarbons, methyl chloroform, and carbon tetrachloride, which can deplete the stratospheric ozone. 

 

Ozone layer: Sits roughly 15km above earth and shields us from harmful radiation from the sun. Natural events and man-made events can produce changes in ozone concentration. The depletion of the ozone layer was once a major concern, but catastrophic harms have largely been avoided.

 

 

P

 

Paris Agreement: The Paris Agreement was adopted on December 2015 in Paris, France. The major goal of the Agreement is as follows: ‘Holding the increase in the global average temperature to well below 2C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5C above pre-industrial levels.’ Critics suggest signatories are drastically failing to meet that pledge.

 

Parts per million/billion/trillion: Number of parts of a chemical found in one million/billion/trillion parts of a particular gas, liquid, or solid mixture. Essential for measuring concentration.

 

Permafrost: Continually frozen ground occurring in temperature remaining below 0C for years.

 

Phenology: The study of the timing of natural events, such as flower blooms and migrations, that are influenced by climate change. 

 

Photosynthesis: How plants take CO2 from the air to build carbohydrates, releasing O2 in the process.

 

 

R

 

Radiation: Energy transfer in the form of electromagnetic waves or particles that release energy when absorbed by an object. Includes ultraviolet, infrared, solar, and longwave radiation.

 

Recycling: Collecting and reprocessing a resource so it can be re-used. Can also refer to the conversion of waste materials into new objects.

 

Reflectivity: The ability of a surface material to reflect sunlight.

 

Reforestation: Planting of forests on lands that have previously contained forests but that have been converted to some other use. Related to afforestation and deforestation.

 

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.

 

Remaining carbon budget: Net global anthropogenic CO2 emissions from the start of 2018 to the moment anthropogenic emissions reach net zero. Would likely limit global warming to a given level.

 

Renewable energy: Energy resources that are naturally replenishing. Examples include, among others,  biomass, geothermal, solar, wind, ocean thermal, wave action, and many more.

 

 

S

 

Scenario: An 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.

 

Sea ice: Ice found at the sea surface that has originated from the freezing of seawater. Sea ice may be discontinuous pieces (ice floes) moved on the ocean surface by wind and currents (pack ice), or a motionless sheet attached to the coast (land-fast ice).

 

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).

 

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.

 

Social costs: The full costs of an action in terms of social welfare losses, including external costs associated with the impacts of this action on the environment, the economy (GDP, employment) and on the society as a whole.

 

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.

 

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.

 

Sustainability: An umbrella term addressing the different aspects of sustainable development. Embedded into this term are concerns for environmental, social, and economic issues.

 

 

T

 

Thermal expansion: Increase in volume (and decrease in density) that results from warming water.

 

Tipping point: A tipping point is a critical threshold beyond which a system must reorganise. In the context of climate change, the tipping point identifies the point in time beyond which certain consequences become irreversible.

 

Trace gas: Less common gases found in the Earth’s atmosphere such as CO2, water vapor, CH4, oxides of nitrogen, ozone, and ammonia.

 

Troposphere: The lowest part of the atmosphere from the surface to about 10 km in altitude in mid-latitudes) where clouds and "weather" phenomena occur.

 

 

U

 

United Nations Framework Convention on Climate Change (UNFCCC): The Convention on Climate Change sets a framework for intergovernmental efforts to tackle climate change. The Convention acknowledges the shared responsibilities. To date, 189 countries have currently ratified the Convention.

 

 

V

 

Vulnerability: Name given for the degree that a system is able to cope with adverse effects of climate change, particularly exploring climate variability and extremes.

 

 

W

 

Wastewater: Water that has been used and contains dissolved or suspended waste materials.

 

Watershed: A land area that channels rainfall and snowmelt to creeks, streams, and rivers, and eventually to outflow points such as reservoir, bays, and the ocean.

 

Water vapor: The most abundant greenhouse gas. It is water in gaseous form. Important in terms of the greenhouse effect, as warming climates lead to increased water vapor – a positive feedback loop.

 

Weather: Atmospheric condition at any given time or place. Weather is generally measured by wind, temperature, humidity, atmospheric pressure, cloudiness, and precipitation.

 

 

X

 

 

Y

 

 

Z

 

Zero-carbon: Zero-carbon refers to a situation in which no carbon is emitted as a result of an activity or operation.