Climate Science Glossary




Afforestation is the process of planting trees, or sowing seeds, in barren land devoid of trees, in order to create a forest.


Also called ‘climate change adaptation’, these are the actions set to cope with the effects of climate change, by addressing real-time consequences.

Amazon rainforest

The Amazon rainforest, covering much of northwestern Brazil and extending into Colombia, Peru and other South American countries, is the world’s largest tropical rainforest, famed for its biodiversity.


There are 43 Parties to the UNFCCC listed in Annex I of the Convention, including the European Union. These Parties are classified as industrialized (developed) countries and "economies in transition" (EITs). The 14 EITs are the former centrally-planned (Soviet) economies of Russia and Eastern Europe.


Of the Parties listed in Annex I of the Convention, 24 are also listed in Annex II of the Convention, including the European Union. These Parties are made up of members of the Organisation for Economic Co-operation and Development (OECD). Annex II Parties are required to provide financial and technical support to the EITs and developing countries to assist them in reducing their greenhouse gas emissions (climate change mitigation) and manage the impacts of climate change (climate change adaptation).

Antarctic Circumpolar Current (ACC)

The Antarctic Circumpolar Current (ACC) is an ocean current that flows clockwise from west to east around Antarctica.

Antarctic ice sheet

The Antarctic ice sheet is one of the two polar ice caps of the Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth. It measures almost 14 million square kilometres and contains 26.5 million cubic kilometres of ice.

Atlantic meridional overturning circulation (AMOC)

The Atlantic meridional overturning circulation (AMOC) is the zonally-integrated component of surface and deep currents in the Atlantic Ocean.




A short form of the phrase ‘biological diversity’, which means the variety of life on this planet and how it interacts within habitats and ecosystems. Biodiversity covers all plants, animals and micro-organisms on land and in water.


All types of energy derived from biomass, including biofuels.


Liquid transport fuels made from biomass.


A source of fuel made from living and/or recently-dead plant materials such as wood, leaves and the biodegradable part of industrial and municipal waste.



Carbon capture and storage

Carbon capture and storage (or carbon capture and sequestration or carbon control and sequestration) is the process of capturing waste carbon dioxide (CO2) from large point sources, such as fossil fuel power plants, transporting it to a storage site, and depositing it where it will not enter the atmosphere, normally an underground geological formation.

Carbon count

A measure of the amount of carbon dioxide you produce through your lifestyle every day, for example through driving or using electrical appliances and lighting


The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and atmosphere of the Earth.

Carbon emissions

The carbon dioxide that is released when substances, especially oil, gas, and coal, are burned by vehicles and planes, by factories and by homes.

Carbon footprint

The amount of carbon emitted by an individual or organization over a given period of time, or the amount of carbon emitted during the production lifecycle of a product.

Carbon neutral

A situation that arises when the amount of carbon dioxide released into the air equals the amount of carbon dioxide removed from the air, e.g. by planting trees, or the amount saved by using renewable energy sources to produce the same amount of energy.

Carbon offsetting 

A way of compensating for emissions of CO2 by participating in, or funding, efforts to take CO2 out of the atmosphere. 


A carbon sink is a natural or artificial reservoir that accumulates and stores some carbon-containing chemical compound for an indefinite period. 

Carbon tax

A tax on fuels according to their carbon content, which aims to encourage people and businesses to use fuels with less carbon and reduce the amount of energy they use.

Clean Development Mechanism (CDM)

The Clean Development Mechanism (CDM) is one of the Flexible Mechanisms defined in the Kyoto Protocol (IPCC, 2007) that provides for emissions reduction projects which generate Certified Emission Reduction units (CERs) which may be traded in emissions trading schemes.

Climate change

A pattern of change affecting global or regional climate, as measured by average temperature and rainfall, or an alteration in frequency of extreme weather conditions. This variation may be caused by both natural processes and human activity. Global warming is one aspect of climate change.


Climate risk means a risk resulting from climate change and affecting natural and human systems and regions.

Climate variability

Changes in the long-term characteristics/trends of weather, or the normal range of climatic variables over a specific climatic period.

Convention on Biological Diversity (CBD)

The Convention on Biological Diversity (CBD), known informally as the Biodiversity Convention, is a multilateral treaty. The Convention has three main goals including: the conservation of biological diversity (or biodiversity); the sustainable use of its components; and the fair and equitable sharing of benefits arising from genetic resources.

Conference of the Parties (COP)

The Conference of the Parties (COP) is the governing body of an international convention, such as within the UNFCCC.


Coral bleaching is the whitening of coral that results from the loss of a coral’s symbiotic algae (zooxanthellae) or the degradation of the algae’s photosynthetic pigment. It is associated with the devastation of coral reefs, which are home to approximately 25 percent of all marine species.




The permanent removal of standing forests that can lead to significant levels of carbon dioxide emissions.




A community of organisms that depend on each other and the environment they inhabit.


In the context of the atmosphere, gases or particles released into the air that can contribute to global warming or poor air quality.

Emission Trading Scheme (ETS) 

A scheme that allows the trading of emissions permits between business and/or countries as part of a cap and trade approach to limiting greenhouse gas emissions. 

Energy efficiency

Actions to save fuels, e.g. better building designs, the development of better transport policies, using better road vehicles and using insulation and double glazing in homes.

El Niño–Southern Oscillation (ENSO)

El Niño–Southern Oscillation (ENSO) is an irregularly periodic variation in winds and sea surface temperatures over the tropical eastern Pacific Ocean, affecting the climate of much of the tropics and subtropics.

Environmental impact statement

A statement about the expected effects on the environment of a proposed project or development, which includes crisis management.



Fossil fuels 

Natural resources, such as coal, oil and natural gas. These resources are formed in the Earth over millions of years and produce carbon dioxide when burnt to become fuel.



Greenland ice sheet

The Greenland ice sheet is a vast body of ice covering 1,710,000 square kilometres (660,000 sq mi), roughly 80% of the surface of Greenland. It is the second largest ice body in the world, after the Antarctic ice sheet. 

Group of 77 (G77)

The Group of 77 (G77) at the United Nations is a coalition of 134 developing nations, designed to promote its members' collective economic interests and create an enhanced joint negotiating capacity in the United Nations.


A glacier is a large, perennial accumulation of crystalline ice, snow, rock, sediment, and often liquid water, that originates on land and moves down slope under the influence of its own weight and gravity.

Global warming 

The steady rise in global average temperature in recent decades, which experts believe is largely caused by man-made greenhouse gas emissions.

Greenhouse gases (GHGs) 

Greenhouse Gases (GHGS) are six natural and industrial gases that trap heat from the Earth and warm the surface. They are: carbon dioxide, methane, nitrous oxide, hydroflourocarbons, perfluorocarbons and sulfur hexafluoride.

Greenhouse effect 

The insulating effect of certain gases in the atmosphere, resulting in solar radiation which warms the earth and prevents some of the heat from escaping.



Hazardous waste

Waste that poses a risk to human health or the environment, that needs to be handled and disposed of carefully, e.g. oil-based paints, bleach and waste electrical/electronic devices.

Hydrologic cycle

The hydrologic cycle, also known as the water cycle or the hydrological cycle, describes the continuous movement of water on, above and below the surface of the Earth.




An ice sheet, also known as a continental glacier, is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi).

Intergovernmental Panel on Climate Change (IPCC)

The Intergovernmental Panel on Climate Change (IPCC) is a scientific body established by the United Nations Environment Programme and the World Meteorological Organization. The IPCC reviews and assesses the most recent scientific, technical, and socio-economic work relevant to climate change and was honoured with the 2007 Nobel Peace Prize.



Joint Implementation (JI)

Joint implementation (JI) is one of three flexibility mechanisms set out in the Kyoto Protocol to help countries with binding greenhouse gas emissions targets (the Annex I countries) meet their obligations. JI is described in Article 6 of the Kyoto Protocol.



Kyoto Protocol / Kyoto agreement

An international agreement signed in Japan in 1997, attached to the UN Framework Convention on Climate Change. Under the agreement industrialised countries promised to reduce their combined greenhouse gas emissions to at least 5 percent below 1990 levels over the period 2008-2012. 



Madden–Julian oscillation (MJO)

The Madden–Julian oscillation (MJO) is the largest element of the intra-seasonal (30-day to 90-day) variability in the tropical atmosphere.

Mass Extinction

The extinction of a large number of species within a relatively short period of geological time, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt.

Mechanical biological treatment (MBT)

Mechanical biological treatment (MBT) is a way of sorting and treating waste. The waste is first sorted into materials that can or cannot be recycled, then any waste that can be recycled is broken down biologically, often through composting, while the rest is sent to landfill. 

Methane clathrate / methane hydrate

Methane clathrate or, also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice.


Action to reduce man-made climate change. This includes addressing the bedrock causes of climate change by creating global policies to counteract the growing variance and consequently enforcing these policies in order to reduce carbon emissions.


The ‘Montreal Protocol on Substances that Deplete the Ozone Layer’ is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. 



Nitrogen Cycle

The nitrogen cycle is the biogeochemical cycle by which nitrogen is converted into multiple chemical forms as it circulates among atmosphere, terrestrial, and marine ecosystems.

Non-Annex I parties (of UNFCCC)

Parties to the UNFCCC not listed in Annex I of the Convention are mostly low-income developing countries. Developing countries may volunteer to become Annex I countries when they are sufficiently developed.

North Atlantic Oscillation (NAO)

The North Atlantic Oscillation (NAO) is a weather phenomenon in the North Atlantic Ocean of fluctuations in the difference of atmospheric pressure at sea level (SLP) between the Icelandic Low and the Azores High.



Ocean acidification

Ocean acidification is the ongoing decrease in the pH of the Earth's oceans, caused by the uptake of carbon dioxide from the atmosphere. 

The OrganiZation for Economic Co-operation and Development (OECD)

The Organisation for Economic Co-operation and Development (OECD) is an intergovernmental economic organization with 36 member countries, founded in 1961 to stimulate economic progress and world trade.

Ozone layer

The thin protective layer of gas 10 to 50km above the Earth that acts as a filter for ultraviolet (UV) radiation from the sun. High UV levels can lead to skin cancer and cataracts and affect the growth of plants.



Pacific Decadal Oscillation (PDO)

The Pacific Decadal Oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin.

Per-capita emissions

The total amount of greenhouse gas emitted by a country per unit of population.


In geology, permafrost is ground, including rock or cryotic soil, at or below the freezing point of water 0 °C (32 °F) for two or more years.



Radiative forcing

Radiative forcing, or climate forcing, is the difference between insolation (sunlight) absorbed by the Earth and energy radiated back to space.

Reducing Emissions from Deforestation and forest Degradation (REDD+)

Reducing Emissions from Deforestation and forest Degradation (REDD+), a concept to provide developing countries with a financial incentive to preserve forests.


Reforestation is the natural or intentional restocking of existing forests and woodlands that have been depleted, usually through deforestation.

Renewable energy

Renewable energy is energy created from sources that can be restored in a short period of time, e.g. biomass (such as wood and biogas), the movement of water, geothermal (heat from within the earth), wind, and solar.

Representative Concentration Pathway (RCP)

A Representative Concentration Pathway (RCP) is a greenhouse gas concentration (not emissions) trajectory adopted by the IPCC for its fifth Assessment Report (AR5) in 2014. It supersedes Special Report on Emissions Scenarios (SRES) projections published in 2000.




Sea levels rose 3.0 mm per year in the 20th century. Since 1990 that rose to 3.4mm. Since 2010 now 4.6mm per year.


Small Island Developing States (SIDS) are a group of small island countries that tend to share similar sustainable development challenges, including small but growing populations, limited resources, remoteness, susceptibility to natural disasters, vulnerability to external shocks, excessive dependence on international trade, and fragile environments. 



Thwaites Glacier

Thwaites Glacier (75°30′S 106°45′W), sometimes known as Pine Glacier, is an unusually broad and fast Antarctic glacier flowing into Pine Island Bay, part of the Amundsen Sea, east of Mount Murphy, on the Walgreen Coast of Marie Byrd Land



United Nations Environment Programme (UNEP)

The United Nations Environment Programme (UNEP), an agency of the United Nations, coordinates the organization's environmental activities and assists developing countries in implementing environmentally sound policies and practices.

United Nations Framework Convention on Climate Change (UNFCCC)

Adopted at the 1992 Earth Summit in Rio de Janeiro, the United Nations Framework Convention on Climate Change (UNFCCC) is one of a series of international agreements on global environmental issues. The UNFCCC aims to prevent hazardous human interference with the climate system. It entered into force on March 21, 1994, and has been ratified by 192 countries.