There are many phrases you might feel you ought to understand when it comes to climate change. With COP26 just around the corner, here are some of the most commonly used terms to help you to get up to speed. 

Afforestation & deforestation

Afforestation means growing new trees in an area where there were none before to create a new forest. This is an example of a natural climate solution (see carbon capture).

Deforestation means chopping down a large area of trees. For example, an area roughly the size of a football pitch is destroyed every minute in the Amazon Rainforest, primarily to clear space for cattle and to grow crops for animal feed. Deforestation reduces the amount of carbon dioxide that can be absorbed from the atmosphere (see carbon sink).


The variety of plant and animal life in a particular environment. The climate crisis is also a threat to biodiversity because it will change many habitats faster than plant and wildlife will be able to adapt. For example, at 2 degrees of global heating, 16% of plants will lose half of their habitable environment.


In the context of climate change, ‘carbon’ is used as shorthand for ‘carbon dioxide’ in terms such as carbon emissions, carbon footprint and carbon capture.

Carbon Dioxide (CO2)

Carbon Dioxide (CO2) occurs naturally and is vital for many eco systems. For example, plants and trees take in carbon dioxide to create energy via photosynthesis, releasing the oxygen that we breathe in the process.

However, carbon dioxide is also released by burning fossil fuels. More carbon dioxide is being released into the in the atmosphere than can be absorbed by the earth’s plant life and oceans. This is a problem because, as a greenhouse gas, carbon dioxide in the atmosphere stops heat energy escaping and causes global heating.

British woodland in autumn.
Carbon emissions

Carbon dioxide released by burning fossil fuels and other industrial processes.

Read about how we work out how much carbon our customers save by switching to renewable energy.

Carbon footprint

The amount of carbon dioxide generated by the activities of individuals and businesses. You can measure your personal carbon footprint to help you spot ways you could be greener, for example by switching to a renewable energy supplier or reducing how much you use your car.

Controversially, the concept of a carbon footprint was actually invented by BP. It’s seen as greenwashing and an attempt to shift the responsibility for tackling climate change onto individual actions, rather than the fossil fuel companies whose products are causing the crisis.

Despite its origins, ‘carbon footprint’ is still a well-known and helpful concept for enabling individuals and businesses to become more aware of green actions they could take.

Carbon capture & carbon sequestration

Reducing the concentration of carbon dioxide and other greenhouse gases in the atmosphere.

Technological solutions include capturing carbon dioxide caused by industrial processes and fossil fuel power stations before it is released into the atmosphere and storing it underground. Natural solutions include regenerating environments that store carbon dioxide, including forests, hedgerows and peatlands.

Carbon offset

Balancing greenhouse gases that are emitted from certain activities by either absorbing emissions elsewhere or preventing an equivalent amount from being emitted. E.g. Paying to plant some trees to balance out the carbon emitted from taking a flight.

The most effective kind of carbon offsetting is investing in projects that prevent carbon dioxide from being emitted in the first place, alongside measures that remove carbon dioxide from the atmosphere. For example, Good Energy invests in Gold Standard projects that focus on replacing solid and fossil fuel use with green energy such as renewable biogas.

Carbon sink

Used to describe natural environments, such as forests and the ocean, that absorb carbon dioxide from the atmosphere.

For example, the clearing of the Amazon Rainforest has reached such an extent that more carbon is released from the trees that are burnt than the rest of the forest is able to reabsorb, turning it from a carbon sink into a carbon source.

Climate change & climate breakdown

Climate change refers to changes in the state of global climate that can be measured over an extended period – usually decades or longer.

The UN Framework Convention on Climate Change (UNFCCC) defines it as ‘a change which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”.

Measurable effects of climate change could include heatwaves increasing in frequency or severity; droughts becoming more frequent or longer lasting; average rainfalls decreasing or increasing; storms, hurricanes and cyclones becoming more frequent and severe

Climate breakdown is a more recent term used to reflect the severity of the impact of carbon emissions. It describes the fact that the climate conditions that have been present for at least the past 10,000 years, during which human civilization has developed, are no longer stable.

Climate crisis & climate emergency

Similarly to climate breakdown, climate crisis and climate emergency have come into use by newspapers such as the Guardian because ‘climate change’ is no longer seen to describe the seriousness of the changes we’re experiencing. They reflect the fact that urgent action is needed to keep our climate safe and stable.

Climate action & climate justice

The UN Sustainable Development Goals defines climate action as ‘stepped up efforts to reduce greenhouse gas emissions and strengthen resilience and the capacity to adapt to climate-induced impacts’ such as severe weather events.

Climate justice frames the climate crisis as an ethical and political issue as well as an environmental one. It acknowledges that people and places will experience the impact of the climate crisis unequally. For example, countries in the Global South are more vulnerable than those in the Global North, and may have fewer resources available for adapting to climate impacts.

To counter this inequality, climate justice calls for the integration of social justice and human rights into policies to limit climate breakdown.

COP (26)

COP stands for the Conference of the Parties, an annual global climate summit that takes place under the United Nations Framework Convention on Climate Change (UNFCCC). Representatives from every country meet to agree targets, responsibilities and action plans for limiting greenhouse gas emissions and avoiding dangerous climate change.

Key COPs in the past have included COP3 in 1997, which resulted in the Kyoto Protocol – an international treaty which committed countries to reduce their greenhouse gas emissions; and COP21 in 2015, which resulted in the Paris Agreement – an international treaty which calls countries to keep global warming under 2 degrees above pre-industrial levels.

COP26 takes place in Glasgow in November, and is the first opportunity for countries to review their commitments since the Paris Agreement took effect, and strengthen their commitments to make sure it can be achieved. Read more about COP26.

Drawdown (climate)

The point at which greenhouse gas concentrations in the atmosphere level off and start to decline.

Fossil fuels

Coal, oil and gas. Formed from the remains of plants and animals that lived and died hundreds of millions of years ago. Burning them releases the carbon that those organisms absorbed while alive and that has been locked up since that time. The increased concentration of carbon dioxide in our atmosphere is causing global heating.

Global warming & global heating

An increase in the overall surface temperature of the earth.

You may have come across the description of global warming being X degrees ‘above pre-industrial levels’. Climate scientists have tracked an upward trend in temperatures since around 1850, when fossil fuel use rapidly increased due to the industrial revolution. This change in temperature makes it clear that the rapid increase in global temperatures that we’re experiencing is caused by human activity. In comparison, natural changes in the earth’s temperature (e.g. changes that brought about ice ages) happen over periods of thousands of years.

Observed and simulated changes in global surface temperature, IPCC Sixth Assessment Report, August 2021.

Global heating has come into use more recently because it more accurately describes the fact that human activity is actively ‘heating’ the planet, rather than the planet simply warming on its own.

Greenhouse gases, greenhouse effect

Gases (including carbon dioxide and methane) in the earth’s atmosphere that prevent some heat energy from escaping – this is known as the greenhouse effect.

The increasing concentration of carbon dioxide and methane in the atmosphere causes more heat to be trapped, raising the average temperature of the earth’s surface.


Achieving an overall balance between emissions produced and emissions taken out of the atmosphere. This is in comparison to gross-zero, which would reduce all emissions uniformly to zero.

The UK has committed to reaching net-zero emissions by 2050.

Renewable energy

Energy sources that are naturally replenished, rather than getting depleted when used. Solarwindhydrotidal and bioenergy are classed as renewable.