Hacking the Earth’s cooling system

Material scientists are working to make the most of a powerful (and energy-free) cooling mechanism.

This year is on track to be the second or third warmest on record, and 2024 was even hotter – the warmest since records began. And beyond global averages, extreme heat events are also on the rise. The Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6) states with an over 99 per cent probability that, since 1950, the frequency and intensity of hot extremes have increased on a global scale.

Already in the first half of 2025, many readers will have experienced first-hand heatwaves in the UK and Europe. Perhaps less well-known is the fact that Central Asia experienced extraordinary unseasonable heat in March, or that extreme heat arrived in Southeast Asia much earlier than normal.

More frequent bouts of hot weather matter, in part, because of their health impacts. The Grantham Institute estimates that the recent European heatwave increased the number of heat deaths by around 1,500 in 12 European cities. Because of this, it’s clear that we need cooling solutions to protect us from the changing climate.

This feature is not just about climate adaptation, however; it is also about climate change mitigation. This is because we already have technologies to help keep us cool, but unfortunately these are polluting and energy-intensive. “As temperatures get hotter, we are actually using a lot of active air conditioning systems that paradoxically make the world even hotter,” explains Sandra Go, co-founder of London-based radiative cooling startup Emissiv. These systems “use a lot of electricity and release harmful refrigerants.”

According to Our World in Data, air conditioning already causes around 3 per cent of global greenhouse gas emissions, and this is only set to increase as previously cool countries like the UK find themselves having to deal with more severe summer heat. According to the International Energy Agency (IEA), the number of air conditioning units in the world is on course to triple by 2050.

We therefore need new ‘passive’ (or energy-free) solutions to break out of what has become known as the ‘cooling paradox’ – where more air conditioning equals more emissions, which equals more heat. Radiative cooling – the emission of infrared radiation in wavelengths that can escape the atmosphere – looks set to provide us with one of those solutions.

With our previous features on mycelium and aerogels, we looked back to the 19th century for the first use of this ‘technology’. However, the Earth has been ‘doing’ radiative cooling for its entire 4.5-billion-year existence. What has changed (and quite recently) is our ability to create materials that manipulate and enhance this natural phenomenon.

In this deep dive, we look at some of the opportunities and challenges associated with radiative cooling. With the help of experts in the field, we outline some of the key points organisations need to understand if they are to explore the technology as a serious and scalable climate solution.