Extraordinary heat waves have readers asking how A/C affects greenhouse gas emissions

An extraordinary heat wave last week toppled thousands of temperature records across Asia, from Iran to Japan. In Iran’s highlands, the city of Isfahan, at the foothills of the Zagros Mountains, sweltered in temperatures up to 43.8 degrees Celsius (110.8 degrees Fahrenheit). Japan, which saw at least 120 deaths due to heatstroke in July, issued more heat stroke warnings August 9, as temperatures climbed to 39° C (102.2° F).

As what’s “normal” for temperatures continues to tick upward, it’s important to note that we can’t just adapt our way out of climate change, scientists have warned. A concerted, global effort to curb carbon emissions is what’s needed to stave off more disastrous climate consequences, researchers say (SN: 2/28/22).

But how do we live with the heat that’s already here? Readers have asked us a variety of great questions about resilience, energy use and adaptations — many of which we aim to answer in future updates. There’s so much to say on this subject.

Several readers asked specifically about air conditioning, so let’s start there. Some of the questions we got include: How much additional carbon dioxide is emitted due to U.S. usage of air conditioners in the summer? How can we lead a life that uses less electricity?

According to the U.S. Energy Information Administration, in 2020 (the most recent data available), air conditioning accounted for almost 20 percent of the total electricity consumption by U.S. homes (or about 254 billion kilowatt-hours). In U.S. commercial buildings, in 2018 electricity consumption for cooling accounted for about 18 percent if the buildings’ total energy use. And another 18 percent of commercial buildings’ electricity consumption was for ventilation — moving the cooled air around.

As for how that translates to carbon dioxide emissions? Air conditioning accounts for about 117 million metric tons of the greenhouse gas emitted to the atmosphere each year, according to the U.S. Department of Energy. Researchers at the U.S. National Renewable Energy Laboratory, based in Golden, Colo., calculated that globally in 2022, air conditioning is responsible for about 1.950 million metric tons of carbon dioxide released each year, amounting to nearly 4 percent of total global greenhouse gas emissions.

That fraction is likely to increase as the world warms — so there are active areas of research into how to cool buildings without cranking up the A/C (and thereby increasing energy consumption). For example, a new study published August 9 proposed a zigzag wall design that would increase the building’s passive radiative cooling ability — in other words, it can reduce the wall’s temperature while also sending more of the sun’s heat back into space at a wavelength not absorbed by Earth’s atmosphere (SN: 8/9/24).

Innovative designs like this — alongside research into how best to cool homes through solar panels, urban tree cover and other strategies — will be subjects for future updates. Stay tuned!