Air conditioning: Can people stay cool without warming the planet?

As heat waves sweep across the Northern Hemisphere this summer, there is increasing attention on what many experts have long warned will be a catch-22 of climate change: As temperatures climb and hot spells last longer, billions more people will need or want air conditioning – and because of expanding economic development, a growing number will be able to afford it.

But air conditioning and electric fans already account for about a fifth of the electricity used in buildings across the world, according to the International Energy Agency. And recent estimates from the National Renewable Energy Laboratory, part of the U.S. Department of Energy, say air conditioning globally is responsible for around 4% of the world’s greenhouse gas emissions.

In other words, as climate