When a heat wave blanketed Europe in early July, it did more than just make for insufferable days and sweat-soaked nights. Scorching temperatures which hit 45C in some places killed more than 2,300 people across 12 cities, according to a new study by Londons Imperial College. Most of those people, the study found, would have lived if not for climate change.
The report underlines what experts say is the mounting threat of extreme heat. Once relatively rare, supercharged temperatures are becoming more common as humanity pumps greenhouse gases into the atmosphere, feeding the climate crisis and leaving urbanites from Toronto to Delhi desperate for ways to escape the heat.
The reality is that our planet is boiling, says Martin Krause, the Director of the Climate Change Division at the United Nations Environment Programme. As extreme heat becomes the new normal, cooling is becoming essential to protect health, jobs, food supplies and even infrastructure.
Heres a closer look at extreme heat and what can be done about it.
What exactly is extreme heat?
The phrase generally describes temperatures well above normal for a given place. So, amid an Antarctic winter, a 0C day would be considered extreme.
But for humans, the real danger arises when the so-called wet-bulb temperature approaches 35C. Wet bulb readings combine heat and humidity into a single value.
At 35C and up, temperatures can compromise the human bodys ability to cool itself by sweating. This heightens the risks of heat stroke, which in extreme cases can cause organ failure and death. Between 2000 and 2019, nearly 500,000 people perished annually from heat-related ailments.
What is driving this extreme heat?
In short, humans are. Since the dawn of the Industrial Revolution, humanity has been burning fossil fuels and filling the atmosphere with greenhouse gases, driving the global average temperature up 1.2C. That might not seem like much but its enough to throw delicate climate systems out of whack and make heat waves more common. For example, research suggests climate change made a deadly 2023 Mediterranean heat wave 100 times more likely to happen.
If the world is getting warmer, why cant we just install a lot more air conditioners?
There are three problems with that. Firstly, billions of people around the world cannot afford to buy and operate air conditioners; for them, that kind of cooling is a distant dream, says UNEPs Krause.
Secondly, air conditioners are voracious consumers of electricity, which is still generated from burning fossil fuels in most places, stoking climate change.
Finally, many types of cooling equipment, like fridges and air conditioners, run on hydrofluorocarbons, synthetic gases that are powerful climate pollutants. Some warm the planet nearly 4,000 times more over a 20-year period than carbon dioxide.
Without major changes, 10 per cent of all greenhouse gas emissions will come from cooling by 2050.
Cooling is essential for the health and well-being of billions, says Krause. The irony is that, right now, as current systems are highly polluting and energy-intensive, its making the problem with extreme heat worse, perpetuating a vicious cycle.
If air conditioning is problematic, what can countries do to counter extreme heat?
There are several things governments can do to reduce heat risks in cities and rural communities while also protecting their people including the most vulnerable - from scorching heat.
To lower temperatures, officials can:
- promote passive cooling strategies, especially those that involve nature, like tree planting;
- enact urban planning standards so that roads, buildings and other infrastructure dissipate heat instead of concentrating it, as they often do now; and
- turbo-charge efforts to phase out fossil fuels and quickly cut down on the use of refrigerants that warm the planet.
To reduce on heat-related illnesses and deaths, countries can:
- establish early warning systems that alert residents of impending heat waves;
- strengthen healthcare systems and roll out action plans for countering the health-related risks of extreme heat;
- scale up sustainable cooling programmes;
- develop and enforce rules that protect workers, especially outdoor labourers, from high temperatures; and
- buttress critical infrastructure, like power plants, hospitals and schools, against rising temperatures.
What is passive cooling?
Its a way to bring down temperatures and limit the need for air-conditioning. Some techniques include planting trees to shade homes, designing city streets so they funnel breezes, insulating homes so they need less air conditioning and painting rooftops white, so they reflect the suns rays.
Experts love these kinds of solutions because theyre effective, cheap and could reduce greenhouse gas emissions by 1.3 billion tonnes by 2050. Thats the equivalent of taking nearly 290 million cars off the road.
What is the United Nations doing about extreme heat?
In 2024, UN Secretary-General Antnio Guterres called on countries to join forces to prevent the planet from becoming a sweatbox. As part of the push, 10 UN entities, including UNEP, have been coordinating their work on extreme heat, developing science and best practices, and helping countries implement cooling-related policies, including many of those listed above. For example, the UNEP-led Cool Coalition is fostering innovation and knowledge exchanges while helping countries roll out practical solution for sustainable cooling.
What happens if the world does nothing about extreme heat?
The results could be disastrous. UNEPs Emissions Gap Report 2024 found that the world was on pace to warm to between 2.6C and 3.1C this century. If that happens, heat waves will become much more intense and more frequent, found a panel of leading climate scientists.
Even if we manage to avoid that fate and put the brakes on warming, we still need to green the cooling industry if we want to make conditions liveable for billions of people around the world, and afford them the very basic right of staying cool, says Krause.
UNEP's work is made possible by flexible contributions from Member States and other partners to theEnvironment Fundand UNEPClimate,NatureandPollutionfunds. These funds enable agile, innovative solutions to climate change, nature and biodiversity loss, and pollution and waste. Learn how to support UNEP to invest inpeople and planet.
The Sectoral Solution to the climate crisis
UNEP is at the forefront of supporting theParis Agreementgoal of keeping global temperature rise well below 2C, and aiming for 1.5C, compared to pre-industrial levels. To do this, UNEP has developed theSectoral Solutions, a roadmap to reducing emissions across sectors in line with the Paris Agreement commitments and in pursuit of climate stability. Key sectors identified are: energy; industry; agriculture and food; forests and land use; transport; and buildings and cities.
