Climate glossary

Climate change is complex. The same can be said about the climate concepts you come across in your work.

This Climate Glossary explains some of the most common ones so you can bring clarity to your climate conversations.

A

Adaptation - Work and initiatives that aim to help people prepare for and and adjust to a world that’s altered by climate change.

Adaptive capacity - The ability of a system to adjust to disturbances and changing conditions in a timely manner to reduce damage and take advantage of new opportunities.

Aerosols - Tiny particles in the air that affect the climate by reflecting or absorbing sunlight. Some cool the planet, others warm it.

Albedo - A measure of how much sunlight a surface reflects. High-albedo surfaces like snow reflect more heat, helping cool the planet.

Anthropogenic - Something that’s caused or significantly influenced by human activity (such as climate change).

B

Biodiversity – The variety of all life on Earth. It includes variations in genetic and functional attributes as well as distributions and abundance within and among species and ecosystems.

C

Carbon cycle – The natural circulation of carbon between the atmosphere, oceans, soil and living things.

Carbon neutral – Balancing carbon emissions by removing or offsetting an equivalent amount.

Circular economy – An economic model keeping materials in the economy through repairing, reusing, recycling and regenerating. It’s contrasted to the take-make-dispose model of a linear economy.

Climate - Average weather conditions over a longer period of time (usually 30 years).

Climate budgeting – A governance approach for planning and tracking public spending to align with climate goals.

Climate finance – Financial resources that are used to mitigate or adapt to climate change.

Climate change – A long-term, ongoing shift in the earth’s temperatures and weather patterns.

Carbon budget – The maximum amount of carbon dioxide humanity can emit to stay within a set temperature limit, like 1.5°C.

Carbon offsetting – Compensating for emissions by paying someone else to pollute less or remove CO2 from the atmosphere.

Carbon markets – Trading systems where carbon credits (tokens representing one tonne of CO2) can be bought and sold.

Carbon footprint – The total greenhouse gas emissions caused directly or indirectly by an individual, organisation or product.

Crescimento verde – A ideia de que as economias podem continuar a crescer enquanto reduzem os impactos ambientais.

Carbon sink – Natural or man-made systems that absorb more carbon than they release.

Carbon removal – Techniques that take carbon dioxide out of the atmosphere, like reforestation or direct air capture.

Climate action plan (CAP) — A strategic roadmap that sets out how a city, region or organisation will reduce greenhouse gas emissions and build resilience to climate impacts. CAPs typically include specific targets, sectoral strategies, timelines and actions to deliver on climate commitments, while aligning with international goals like the Paris Agreement.

Climate justice – A principle that highlights how climate change unfairly impacts those least responsible and calls for fair solutions.

COP – An annual Conference of the Parties to one of the United Nations conventions. The ‘Parties’ are the countries that have signed the convention. The three most important environmental conventions are on climate change (UNFCCC), biodiversity (UNCBD) and desertification (UNCCD).

Co-benefits – Outcomes that support multiple goals at once, like improving air quality while reducing emissions. Also known as a ‘win-win’.

Common but differentiated responsibilities and respective capabilities – A core principle of the UNFCCC that acknowledges that all countries share the responsibility for addressing climate change, but their obligations and capabilities to do so differ based on i.a. historical responsibilities and current economic and technological capabilities.

Concessional finance — Finance that is provided below market rates. It’s used to describe a range of below-market-rate financial products such as loans with low interest rates or guarantees.

Conditional funding — Funding that’s only provided if the recipient fulfills specific conditions.

CO2 - Carbon dioxide is a greenhouse gas that heats the atmosphere. We humans have, primarily the burning of fossil fuels, increased the atmospheric concentration of CO2 by over 50% since the industrial revolution (from 278ppm to 427ppm as of February 2025).

Critical minerals – Essential raw materials used in clean energy tech like solar panels, wind turbines and batteries.

D

Decarbonisation – The process of reducing carbon emissions from sectors like energy, transport and buildings.

Degrowth – A movement founded on the premise that economic growth cannot be sustained infinitely on a finite planet. It promotes a planned reduction of energy and resource use designed to bring the economy back within planetary boundaries in a way that reduces inequality and improves human well-being.

E

Earth system – The complex web of physical, chemical and biological components that keep the planet stable and habitable.

Ecocide – Unlawful or wanton acts committed with knowledge that there is a substantial likelihood of severe and either widespread or long-term damage to the environment

Electrification – The process of making a thing or process run on electricity as opposed to some other source of energy, often the burning of fossil fuels.

Energy transition – Replacing fossil fuels with renewables in energy systems.

Exposure – The presence of people or assets in places vulnerable to climate impacts like flooding or heatwaves.

Extreme weather events – An extreme weather event describes weather that’s unusual in terms of magnitude, location, timing or extent. Examples include heatwaves, floods, wildfires, droughts and storms.

F

Fossil fuels – Carbon-rich, non-renewable materials found in the earth’s crust and used by humans to generate heat and energy. They include coal, oil and natural gas. When burned, fossil fuels release greenhouse gases into the atmosphere.

G

Greenhouse gases (GHGs) – Gases that trap heat in the earth’s atmosphere (known as the greenhouse effect). The most important greenhouse gases affected by human activity are carbon dioxide (CO2), methane (CH4) and laughing gas (N20). Water vapour (H20) is the most abundant greenhouse gas in the atmosphere.

Green growth – The idea that economies can continue to grow while reducing environmental impacts.

Green jobs – General description for roles that contribute to mitigating and adapting to climate change or protecting or restoring the environment.

Greenwashing – Making false, undocumented or misleading claims about the environmental benefits of a product or practice.

H

Hazard – A climate hazard is a climate event (like a flood, storm or heatwave) that has the potential to cause harm.

Heat island effect – The tendency for cities to become hotter than nearby rural areas due to replacing natural surfaces with heat-absorbing materials like roads and buildings.

I

Indigenous and local knowledge – A cumulative body of knowledge developed by Indigenous peoples over generations that’s evolving by adaptive processes and are deeply rooted in local environments.

IPCC – Intergovernmental Panel on Climate Change. A body of the United Nations created to provide policymakers with regular scientific assessments on climate change.

IPBES – Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. An independent intergovernmental body established by States to strengthen the science-policy interface for biodiversity and ecosystem services for the conservation and sustainable use of biodiversity, long-term human well-being and sustainable development.

J

Just transition – The idea that the transition to a greener global economy should happen in a way that is fair to everyone, particularly those who have been marginalised, and leaves no one behind.

K

L

Land-use change – A process by which human activities transform a natural landscape into something else. It’s often used to describe the process of turning a natural environment into a human-dominated one, such as cities or agricultural areas.

Loss and damage – The negative impacts caused by climate change despite mitigation and adaptation efforts. It included both economic and non-economic harms.

M

Methane – A potent greenhouse gas released from livestock, waste and fossil fuel extraction. It has 80 times the warming potential of CO2 over a twenty year period.

Mitigation – Action that reduces the severity of climate change by reducing or preventing greenhouse gas emissions or removing greenhouse gases from the atmosphere.

MtCO₂e - Stands for million tonnes of carbon dioxide equivalent. It’s a way to measure all greenhouse gases in a single unit, based on how much they contribute to global warming compared to CO₂.

N

Nationally Determined Contributions (NDCs) – A national climate action plan by each country under the Paris Agreement. They include both mitigation and adaptation efforts. The NDCs are formulated by each country on a voluntary basis. The NDCs are updated and taken stock of every five years.

Natural capital – The stock of natural assets (like forests, water and soil) that provide essential resources and services that underpin human societies.

Negative emissions technologies (NETs) – Human-made technologies that can potentially remove more carbon from the atmosphere than they emit.

Net zero – Getting emission levels to as close to zero as possible, with any remaining emissions able to be reabsorbed by the atmosphere.

Nature-based solutions – Solutions that use the strategic protection, restoration or management of ecosystems to solve societal challenges.

National Adaptation Plans (NAPs) – National-level strategies to identify climate risks and build resilience.

O

Ocean acidification – When oceans absorb CO2 they become more acidic. This threatens marine life and coral reefs.

P

The Paris Agreement – A legally-binding international climate treaty that was agreed at COP21 in Paris in 2015 and came into force the year after. It was signed by 195 countries.

Planetary boundaries – The safe limits for human pressure on the nine critical processes which together maintain a stable and resilient Earth.

Pre-industrial – The time before large-scale industrial activity, and the connected burning of fossil fuels, began. It’s usually used as a baseline for climate comparisons and often defined as the years 1720-1800 or 1800-1850.

Q

R

Rapid-onset events - Climate hazards that develop quickly over hours or days. Intense rainfall, coastal floods, storms, forest fires, landslides and heatwaves are examples of rapid-onset events.

Renewable energy – Energy from naturally replenishing sources like the sun, wind and water.

Reforestation – Planting trees where forests have been cut down, helping store carbon and rebuild ecosystems.

Resilience – The ability of a system to resist, absorb, accommodate, adapt to, transform and recover from the effects of disturbances in a timely and efficient manner.

Retrofitting – Updating old buildings, transport or infrastructure to make them more energy-efficient or climate-resilient.

Risk – The likelihood of negative impacts from a climate hazard. It is the product of the level of hazard and the level of vulnerability.

S

Slow-onset events - Long-term climate hazards that develop gradually over years or decades. Rising sea levels, desertification and rising average temperatures are examples of slow-onset events.

Sustainable Development Goals (SDGs) – The UN’s 17 Sustainable Development Goals published as part of the 2030 Agenda for Sustainable Development that was adopted by all United Nations member states in 2015. The goals underline the need for countries to address social, environmental and economic issues simultaneously.

T

Tipping points – Critical thresholds where a small change triggers a much larger change. Tipping points tend to trigger change that’s abrupt, self-perpetuating and irreversible.

Triple crisis – The interlinked global crises of climate change, biodiversity loss and pollution.

U

UNCBD - United Nations Convention on Biological Diversity. The main international convention for addressing biodiversity loss since 1992.

UNCCD - United Nations Convention to Combat Desertification. The main international convention for addressing desertification since 1994.

Unconditional funding —

UNFCCC – United Nations Framework Convention on Climate Change. The main international convention for addressing climate change since 1992.

V

Vulnerability – Describes how susceptible an individual, a community or a system is to harm from a climate hazard.

W

Water cycle – The continuous movement of water on Earth through processes like evaporation, condensation, precipitation and runoff. Climate change disrupts the water cycle which leads to more frequent, intense and prolonged floods and droughts.

Wet bulb temperature – A combined measure of heat and humidity. It indicates the lowest temperature to which air can be cooled through evaporation (such as perspiration). It gives a fuller indication of when conditions are dangerous for human health. Humans become unable to regulate their body temperature at web bulb temperatures of 35°C.