The effects of global warming are already bringing harm to human communities and the natural world. Further temperature rises will have a devastating impact and more action on greenhouse gas emissions is urgently required.

Population and climate change are directly linked. Every additional person increases carbon emissions — the rich more than the poor — and increases the number of climate change victims – the poor more than the rich.


"All options need to be exercised... We can make choices about how much of each option we use... but the idea you can leave anything out is impossible."

– Intergovernmental Panel on Climate Change, 2018

Population and CO2 emissions

The climate change threat

Further warming of our atmosphere is now almost impossible to avoid. The effects of that warming will depend on how high and how fast the temperature rises. Global warming changes weather patterns, causing severe weather events, heatwaves, droughts and floods.

Climate change is already shrinking glaciers and ice caps, altering the availability of fresh water. It contributes to ocean acidification, destroying coral reefs and other aquatic ecosystems. It makes places uninhabitable for some plants and animals, leading to extinctions and redistribution of species, threatening food production with alien pests and diseases.

Its potential human cost is catastrophic. A rise in sea levels threatens hundreds of millions of people in coastal communities and cities across the globe. Food and water shortages and conflict over productive land will arise, while progress in global health could be rolled back by communicable diseases such as malaria reaching places they never existed before. Hundreds of millions of people are likely to be forced to migrate from their homes by 2050.


Climate change action


“Globally, economic and population growth continued to be the most important drivers of increases in CO2 emissions from fossil fuel combustion.”

Intergovernmental Panel on Climate Change, 2014

The UN projects that without further action to limit population growth, there will be two billion more people by 2050, and three-and-a-half billion more by 2100.

Reducing the number of people being born cuts future carbon emissions, effectively, simply and permanently. That is not the only action needed - technological solutions, personal lifestyle changes, policies to end fossil fuel use and develop alternative energy and potentially fundamental changes to our economic ssytems are all vital. The positive impact of each of those, however, is reduced and may even be completely cancelled out by adding emissions from hundreds of millions of new people as our population increases.

The 2019 Scientists' Warning of a Climate Emergency, signed by more than 13,000 scientists from around the world, explicitly calls for "bold and drastic transformations" regarding both economic and population policies, including making family planning services available to all and achieving full gender equity.

Individual actions

A study published in 2017 by the Universities of Lund and British Columbia suggested that the single most effective measure an individual in the developed world could take to cut their carbon emissions over the long term could be to have one fewer child. While future per capita carbon emissions are impossible to predict, illustrative figures produced by the authors suggested it could be more than 20 times more effective than the next most effective measure, living without a car. (For more information on the study and its methodology, click here.)

All the benefits of this action are not immediate and it does not mean that we should not take other actions to cut our individual carbon footprints, of course. Choosing a small family can make a vital contribution, however.

Tonnes of CO2 saved through environmental actions

Global policy

Another major international study in 2017 identified practical policy measures that could be taken to minimise greenhouse gas emissions as quickly as possible. Project Drawdown analysed more than eighty policy options, such as plant-based diets, solar farms and electric vehicles.

The study identified family planning and educating girls as among the top 10 workable solutions to combat climate change available today. It found that together, they would reduce CO2 emissions by 103 gigatons by 2050 — more than onshore and offshore wind power combined.

Their enormous positive effect is a result of their proven effectiveness in reducing family size and population growth.


Population action

Because individuals in the developed world have the greatest impact each, people choosing to have smaller families in the richest parts of the world will have the greatest and most immediate positive effect – a vital choice given the urgency to address which climate change. Furthermore, reduced emissions as a result of fewer people being born in richer countries allows more economic development in poorer countries without adding to total emissions.

However, in poorer countries, including those where population growth is highest, economic development is increasing individual carbon footprints and rapidly growing populations push emissions still higher. In its landmark 2018 report, the International Panel on Climate Change specifically identified high population growth as a "key impediment" to hitting the critical target of limiting global warming to 1.5°C.

Nations with very high populations such as India and China are among the most significant contributors to climate change overall, despite relatively lower impacts from each individual. While India and China have relatively low population growth, people born today in countries whose populations are still expanding rapidly will have a climate impact for generations to come.

Population growth must be addressed in all countries to tackle climate change.

There are many ethical, effective means of achieving a sustainable population. In addition to family planning, girls’ education and other measures to empower women, people need to be educated about the personal and global benefits of smaller families, while beliefs and values favouring large families must be overturned. All these measures will help reduce family size and bring population growth to an end as soon as possible - giving us all the best chance of limiting climate change and protecting the next generation.

If we are to succeed in preventing the worst effects of climate change, we must take action to address population size.


In 2018, Population Matters hosted a conference, More feet, more heat: climate change and us, which brought together a international panel to examine the relationship between climate change and population. Watch our director's presentation.

More Feet, More Heat: Climate Change Conference 2018

Population Matters's director Robin Maynard speaking at our conference on climate change and population in London, 2018.

Press global leaders for action

20,000 scientists have now signed up to a Warning to Humanity, calling on governments to take action to avert environmental catastrophe. So far, governments have paid little attention. You can support the scientists' campaign.