Air conditioning systems around the world have the potential to produce more carbon dioxide a year by 2050 than the US does today, researchers have said.

The study from a team at the University of Birmingham anticipates that air con usage will double over the next 25 years as increasingly high temperatures force people to remain indoors to stay cool. Even mid-range predictions suggest that electricity for cooling could reach 4,493TWh annually, and in the worst case be responsible for more carbon emissions globally than the modern-day US.

Today, regions that need cooling the most, such as South Asia and Africa, have the least access to air con whereas wealthier regions such as Europe and North America have lower cooling needs but higher usage.

In future, most of the extra emissions are expected to come from higher usage in developing countries as incomes continue to rise. 

Researchers estimate that air conditioning use will add 0.03°C to 0.07°C of global warming by 2050, depending on the emissions pathway the world follows. This is the equivalent of around 74 billion to 183 billion transatlantic return flights. 

Professor Yuli Shan, co-author of the study, said: “Global warming is raising temperatures and causing more heat waves, and economic growth in some of the worst-affected countries means more people can offset extreme heat with air conditioning.

“As global temperatures rise, we risk being locked into an ‘arms race’, where defending ourselves against extreme heat is causing the issue to get worse. The world must transition quickly to cleaner, more efficient cooling technologies – while ensuring fair access to cooling, especially for vulnerable populations.”

As well as adopting a rapid transition to clean electricity, the research team recommends the fast adoption of low‑pollution cooling liquids in air con systems’ refrigerants and better building design – using insulation and shading more effectively. Researchers also advocate for behavioural changes such as turning the air con down and shifting cooling away from peak hours.

Dr Hongzhi Zhang, co-author of the study, said: “The study reveals that if all low‑income regions gained the same access to air conditioning as rich regions, related global emissions would jump dramatically – adding up to 0.05°C extra warming even in the most climate‑friendly scenario.”

Last year, researchers in Australia unveiled a nanoengineered polymer coating that, when applied to a roof, passively cooled the building and captured water directly from the air – without the need for any energy input.