Cooling the world without heating the planet

Climate change is already bringing higher average temperatures and an increased number of heatwaves. Societies need to plan now for how they will keep people comfortable, healthy and economically productive in these temperatures, and to do so sustainably.

The Oxford Martin Programme on the Future of Cooling is applying interdisciplinary research methods to help steer the world towards sustainable cooling for all, and to establish cooling as a global priority for governments and organisations.

It is working to help get us on track to a future where people can live and work comfortably in hot weather, without contributing to further climate change by burning fossil fuels to power energy-intensive cooling systems.

rising temperatures

People around the world are living with higher temperatures as the climate changes, and these effects are not limited to countries used to warmer climates.

For example, Northern European countries will require large-scale adaptation to heat resilience faster than other countries because buildings are mainly prepared to keep people warm during cold seasons. The Future of Cooling team’s research shows that Switzerland and the UK will see a 30% increase in uncomfortably hot temperatures, while Norway will see an increase of 28%.

The researchers stress that this is a conservative estimate and does not consider extreme events like heatwaves or urban heat island effects. Climate change is driving up the likelihood of heatwaves occurring, as well as increasing their duration and maximum temperatures.

In 2023 heatwaves have already driven record temperatures in Russia, China, Vietnam, Laos, Greece, Sardinia in Italy, and Las Vegas and Death Valley in the US.

Cooling Map 2023

The need for cooling


Cooling is necessary for the health and quality of life of billions of people around the world. Extreme heat increases the risk of heart attacks, strokes and other cardiovascular diseases, exacerbates chronic conditions, and can lead to dehydration, heat exhaustion, and even death, especially in vulnerable populations - it is estimated that there were over 60,000 heat-related deaths in Europe in 2022.

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There is also a growing body of evidence that violent crimes increase in hot weather. Murders, sex offences, violent assaults and even suicides all increase as the temperature rises. But many of the physical and mental health impacts of extreme heat exposure are still being researched.

The body can adapt quite well to the temperature changing gradually by 1 or 2°C, and people create social and physiological adaptations. We see this in people moving countries, for example from a temperate climate to a tropical one, when the body requires time but eventually becomes acclimatised. However, there is less ability for the body to adapt to extreme, sudden changes like intense heatwaves. That is when we most need to look to cooling technologies to help us reduce the health impacts of heat and high rates of mortality.

Economic impact

The health of individuals also impacts the economy, and if people are experiencing negative health impacts of heat they may not be able to work. Increased health impacts from heat also increase costs to health services through increased emergency room attendance and demand for ambulances.

Just being uncomfortably hot can affect the productivity of individual workers, as they will need to take more breaks to ensure they are hydrated and do not become unwell. The more physical the job, the more likely workers are to need to prioritise their health over their workload, and outdoor workers will need to take breaks in the shade or in cooler indoor environments.

"Climate change-related heat stress will reduce outdoor physical work capacity on a global scale," the UN's Intergovernmental Panel on Climate Change (IPCC) said in its most recent synthesis report, noting that, by the end of the century, in some tropical regions outdoor work may become impossible for 200 to 250 days each year.

There are also tolls on transport systems, especially in countries like the UK where things like roads and train lines have been built to withstand the country’s previous high summer temperatures, not the new highs driven by climate change. For example, the UK’s rails have a stress-free temperature of 27°C and can start to buckle in temperatures over 30°C. This has economic impacts through travel disruption and the cost of replacing and repairing rail lines. Melting tarmac roads and other damage to infrastructure have similar impacts.

The economic impacts of heat also hit unequally. Taking time off due to heat-related illness and transport disruption will be most harmful to people paid hourly or in unstable employment. Globally, poorer economies experience the worst economic impacts from extreme heat, and this is compounded by the fact that they are also likely to see the highest increases in overall hot days as we approach 2°C of global warming.

Cooling: an essential consideration

Growing international demand for cooling is set to drive one of the most substantial increases in greenhouse gas emissions in history – but the risks and benefits of sustainable cooling have been a global blind spot.

Cooling is not mentioned at all in the UN’s 2030 Agenda for Sustainable Development, the 17 Sustainable Development Goals (SDGs) or in its 169 targets.

This is despite the fact that greener cooling systems could help achieve all 17 goals because extreme heat dramatically affects everything from food production to water quality to students’ ability to learn and focus during school.

The ten countries that will experience the highest increase in need for cooling in a 2.0°C scenario are all in Africa, with central Africa most affected. This will pose further stress to the continent's socio-economic development and energy networks, making cooling a key climate justice and equity issue.

In Rio de Janeiro there are 1.5 million people living in informal settings (favelas). Cooling poverty may force these people to adopt inefficient and potentially hazardous cooling appliances such as second-hand air conditioners or water tanks, which pose health risks and could facilitate the spread of mosquito-borne diseases.

In Northern Europe and other countries including Canada and New Zealand, buildings were not designed to keep out excessive summer heat.

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Residential houses at Mount Victoria in Wellington, New Zealand

These countries are often dangerously unprepared to keep their populations cool in the face of increasing temperatures and heatwaves, and face a massive economic and practical challenge in retrofitting cooling interventions across the built environment. There is also the high risk that countries like these will turn to air conditioning as an off-the-shelf solution for their cooling needs instead of considering a range of sustainable and passive options.

Across the world demand for cooling is increasing and will continue to increase. The key is ensuring this cooling is delivered in a sustainable way that meets societal needs and enables economies to thrive.

Air conditioners: the uncool truth

The energy needed for air conditioning is likely to triple by 2050, with ten new air conditioning units projected to be sold every second until 2050. This huge demand has the potential to drive up greenhouse gas emissions and therefore further exacerbate the very problem it is designed to alleviate.

That is because air conditioners are very energy intensive, and the more fossil fuels we burn to power air conditioners, the worse we make the climate crisis that is driving increases in hot weather and cooling demand. In times of very high demand, this can also stress energy grids, leading to energy shortages or the need for difficult decisions, such as when the UK fired up a coal power plant in June 2023 to meet air conditioning demand.

Air conditioners can also contribute to increased heat within localities and cities. Although they cool the inside of buildings, they pump hot air out of the building and into the streets and surroundings. Many air conditioners doing this all at once can add to the “urban heat island” effect.

Finally, fluorinated gases (F-gases) used as refrigerants can leak into the atmosphere from air-conditioning units. These gases contribute to global warming up to 22,800 times more than the same amount of carbon dioxide in the short term. These F-gases need to be phased out following the Kigali Amendment to the Montreal Protocol, and highly penalised so that Net Zero units that use sustainable natural refrigerant gases, like propane, ammonia or isobutane, can take centre stage.

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The Oxford Martin Programme on the Future of Cooling

The Oxford Martin Programme on the Future of Cooling focuses on creating solutions to influence the trajectory of the future of cooling. This includes transitioning technologies and cooling behaviours that determine energy demand, understanding the implications of severe heat for morbidity and the potential to mitigate negative health effects, and mapping the unaccounted-for impacts of the global cooling production network, including refrigerant gases.

A sustainably cooled future

Passive cooling techniques – from textiles that keep our bodies cool to increased shade in city centres – can be very effective solutions to keep people comfortable as temperatures rise. Many of these have a long history of use in hotter climates around the world.

In homes and other buildings, creating a barrier between the interior and the sun’s rays can be very effective. For example, using external window shutters can reduce cooling needs (the thermal energy required to keep people comfortable) by up to 14%. Even something as simple as painting your roof a light colour can reduce indoor temperatures. Research in very hot cities in Pakistan found that this approach can reduce cooling needs by more than 7%.

In traditionally temperate climates buildings are often poorly ventilated, which makes sense to keep them warm in winter, but with climate change this will be an essential adaptation. For existing buildings, one effective way to cool down is to open windows when the outside temperature drops, for example overnight. This lets warm air escape and invites cooler air in. Buildings can also be “cross ventilated”, where a fresh breeze enters through an opening and exits through another on the opposite side.

When designing new buildings, however, additional features should now be considered to enable the building’s internal temperature to be managed more sustainably in hot weather. Ventilation chimneys and roof vents can be incorporated into building design. These features are often found in hot and arid climates, particularly in the Middle East. Historically, buildings in this region made use of tall, chimney-like structures called wind catchers that capture cool prevailing winds and redirect them into homes.

Inner courtyards have been used for centuries, in places ranging from Ancient Rome to 19th century Morocco, to keep buildings cool. They encourage cross ventilation and can reduce the total amount of time in which we need to take measures to cool down (known as indoor discomfort hours) by 26%.

Beyond buildings, we can do a lot to make cities more comfortable. City streets shaded by trees or awnings, with more plants, green spaces, bodies of water and fountains would help keep the air cooler. The shade from trees and awnings not only provides refuge for people in cities, but also prevents materials like asphalt and concrete from heating up under the sun and adding radiative heating to the city environment. Trees have been found to reduce land surface area temperatures in cities by up to 12°C. This can, in turn, help keep buildings cooler and research in Melbourne, Australia has shown that trees covering buildings in shade can lower the surface temperature of walls by up to 9℃.

Trees, plants, and fountains also help directly cool the environment. Water is very effective at cooling through evaporation, absorption of heat and transport of heat. Flowing or moving water has a greater cooling impact than still ponds, and spray, for example from fountains or misters, is even more effective.

By combining these ideas we can build or retrofit urban environments to be much more comfortable in hot weather. Many of these concepts also have positive knock-on benefits for pollution and biodiversity, which make them even more desirable.

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Wind catcher towers in Yazd, Iran

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The central courtyard of a villa in ancient Pompeii

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A fountain surrounded by trees in downtown Columbia, South Carolina, USA

How can I look after myself in hot weather?

Drink Water

Drink plenty of water

Dehydration is a serious risk and can contribute to other heat-related illnesses


Stick to the shade

Stay out of direct sunlight, particularly between the hours of 11am and 3pm

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Keep your head and hands cool

Think about using things like personal fans and cool compresses

Hat Sunblock

Protect yourself from the sun

Make sure you wear a hat and sunblock if you go outside


Wear lightweight clothes

They should allow air to circulate so consider natural fabrics like linen and light cotton

Take It Easy

Keep strenuous activity to a minimum

Avoid overexertion in the hottest parts of the day

How do we get to a sustainably cooled future?

Change is needed across sectors, governments as well as from individuals to achieve a future where sustainable cooling keeps people comfortable without further contributing to the warming climate.


National and local governments need to consider heat resilience plans. These should focus on ensuring that in cases of extreme heat energy grids are not overloaded by energy-intensive cooling options like air conditioning, the impacts of heat on infrastructure are managed, and that solutions are in place to protect the most vulnerable in society.

Children, the elderly, outdoor workers, and those with existing health conditions are the most at risk from ill-health or death in extremely hot weather and there should be plans to ensure that risk is minimised as much as possible. These plans could include shifting working patterns for outdoor workers so they finish work before the hottest part of the day, creating “cooling hubs” in communities and care homes where vulnerable people can get respite from the heat, or ensuring there is capacity in the healthcare system to meet the additional needs created by extreme heat.

Over the long term, these plans should look at things like the regulations around materials used in buildings and transport infrastructure to ensure their resilience in a warming climate. They should also promote the use of passive or low-energy cooling technologies as well as increasing renewable energy availability and improving the energy grid to ensure there is enough power from clean sources. City and building planning requirements should also be considered to ensure it is easy for individuals, organisations, and local authorities to make improvements.

In the UK, The Environmental Audit Committee is undertaking an inquiry into heat resilience and sustainable cooling in response to a presentation from the Future of Cooling team in early 2023. It sought written evidence in August 2023 and will hold oral evidence sessions in September and October to form an initial view of the issues. Other countries and localities should consider undertaking similar processes.

Most importantly, policy makers should redouble efforts to achieve Net Zero as soon as possible. The only real solution to rising temperatures and increasingly dangerous heatwaves is to solve the climate crisis.

Organisations and businesses

Where organisations have their own building stock they should invest in adapting them to more passive cooling techniques, which would keep their employees cool, reduce their carbon footprint, and reduce cooling costs. Key is to focus on cooling people rather than the space – for example, thinking about more personal cooling devices or other solutions like relaxing the dress code to enable workers to create their own comfort.

Where organisations have rented office space, they should specifically look for and ask for more sustainable options rather than relying on air conditioning – which also comes with higher energy bills the more work it needs to do.

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Businesses directly engaged in cooling, such as manufacturers, should start to rethink their product offering and business models to maximise the economic, social and environmental benefits for owners and users. For example, by offering cooling as a service rather than a product, suppliers would ensure ongoing income while enabling greater investment in longer life and cooling systems with a lower environmental impact. This would also enable a circular economy for cooling systems whereby operators could reduce their overall manufacture of systems without losing profits, reuse systems when they are still working well but their users upgrade, repurpose components of decommissioned systems as spares or refurbish them, and finally recycle old systems into materials for new systems.


Anyone can make a change towards promoting more sustainable cooling solutions, from adopting them in your own home to informing people about the vicious cycle of air conditioning. You can ask those with the responsibility for decisions about cooling, either in businesses you’re involved with or in your country’s government, how they are planning to meet cooling needs sustainably in the future and reach net zero. You can join tree-planting or urban greening projects to create an environment that is better adapted to heat. Individuals can also choose not to be part of the vicious cycle of air conditioning, or only to buy next-generation air conditioners that use less energy and avoid planet-warming refrigerants.

Research organisations, funders and academia

We still do not know enough about the health impacts of heat, the best approaches to cool cities and people, what policies could make the biggest difference, and how to predict and manage extreme heatwaves. As we accelerate beyond 1.5°C of warming above preindustrial temperatures more and more people around the world will face increased cooling needs and risks associated with hot weather. According to Sustainable Energy for All, as the world warms around 30% percent of the global population is exposed to life-threatening heat for at least 20 days a year. As much as investment in research to help us reach Net Zero emissions as soon as possible is needed, we also need investment in understanding how we adapt to a changed planet whatever temperature we manage to limit warming to. It’s essential that research and innovation in these areas is also prioritised.