Why air conditioners can be a problematic solution to extreme heat

As extreme heat hits many parts of the world amid a warming climate, millions of people are turning to air conditioners for relief.

Research shows that household air conditioning is one of the "most effective adaptation strategies to reduce heat-related mortality and morbidity," says a Statistics Canada report released this week. That's particularly the case for older adults and vulnerable populations such as those with mental illness.

But researchers who study climate adaptation say it can also be an unsustainable and problematic solution to extreme heat.

Anabela Bonada, manager and research associate at the Intact Centre on Climate Adaptation at the University of Waterloo, said air conditioning is "absolutely necessary" for vulnerable people who cannot leave their homes.

But, she said, it's a short-term solution and should be "the last resort — because it leads to more heat, which is what we're trying to avoid."

A study published in The Lancet in 2021, led by Ollie Jay, a professor of heat and health at the University of Sydney in Australia, described air conditioning as a "widespread but unsustainable cooling solution."

"It's unsustainable if we want to air condition everybody," Jennifer Vanos, associate professor in the School of Sustainability at Arizona State University and one of the study's co-authors, said in an interview with CBC News.

The study cited a number of reasons for that.

It heats up cities and the Earth in a few different ways. Firstly, air conditioners are heat pumps that move heat from the inside to the outside of a building. Bonada said that means heat from thousands of homes "is being pumped back out into the city, which is already hotter than surrounding areas."

Many air conditioners contain refrigerants called HFCs or hydrofluorocarbons, which can cause far more global warming per kilogram than carbon dioxide.

However, most of their global warming impact comes from the amount of electricity they use in places with fossil fuel-powered generation. According to the International Energy Agency (IEA), indirect emissions from space cooling have tripled between 1990 and 2021 to more than a gigatonne.

It's not very accessible to those who need it most. The cost of buying and running air conditioners tends to make them unaffordable to the most vulnerable.

The Statistics Canada study this week said that while air conditioners were in 61.1 per cent of Canadian homes in 2017, people were far less likely to have them if they had less than a high school education, lived alone or did not own their own homes.

The Lancet study found even bigger disparities in countries like China, especially among those older than 65 and living in rural areas.