If you were under the impression that air conditioning has much less environmental impact than it did 20 years ago, you'd be both right and wrong.
Years ago, chlorofluorocarbons (CFCs) from A/C units contributed to a hole in the Earth's ozone layer. After some resistance, government and industry finally came together to fight the problem via 1987's Montreal Protocol, which led to an agreed-upon phaseout over time by more than 200 countries. In the U.S., the Environmental Protection Agency's final rule on the subject was passed in 1992, and by 2000 CFCs were totally phased out of air conditioning units.
Those CFCs were replaced by hydrofluorocarbons (HFCs), though, and while they don't exacerbate the hole in the ozone layer (which is slowly-but-surely closing up), they do impact climate change. They account for only 1 percent of global greenhouse gas emissions, but they have an outsized impact in comparison to their overall volume. They're thousands of times more impactful than CO2, so even small amounts contribute to climate instability.
Even more worrisome, HFCs could make up almost 20 percent of emissions by 2050. That's because air conditioning use is growing rapidly due to a number of factors, including "being driven by demand from emerging economies, hot climates, and rising incomes that are also undergoing rapid urbanization and electrification," according to research out of the Lawrence Berkeley Laboratory, which recently published a report on the subject.
For perspective, less than 10 percent of homes in India have A/C, but 40-60 percent of electricity used in big cities comes from A/C. And A/C units by the billions are expected to be installed in Asia and Africa by the middle of the century.
“If one is thinking about energy and environment in the next couple decades, you have to think about cooling,” Lukas Davis, an associate professor at the Haas School of Business at the University of California, Berkeley told the New York Times. And while A/C is an on-the-ground way to fight hotter temperatures in the short term, the warmer it gets, the more A/C is needed, creating a vicious loop. Preventing warming as much as possible is a more effective way to deal with the issue, but we can't eliminate air conditioning in many cases (though conservation is an important part of the puzzle).
Where to start
We can change what chemicals are being used to create those cool blasts of air, which is the goal of the Kigali Amendment, an amendment to the Montreal Protocol, which aims to phase out HFCs. And we can work to make air conditioning units more efficient so that they use less energy.
The good news is that the Kigali Amendment, named for the city in Rwanda where it was signed last year, seems to be moving forward, with both government and industry supporting it. But because the United States is now a footnote on such agreements (thanks to the fact that the U.S. has signaled its plans to withdraw from the Paris Climate Agreement), changes may not be seen here.
According to the New York Times: "The State Department has neither sent the Kigali Amendment to the Senate for ratification as a treaty nor ruled that the deal does not require a legislative green light. A spokesman said the department had no updates on the matter. At least one powerful lawmaker, Senator James M. Inhofe, Republican of Oklahoma, has vowed to oppose the amendment if it gets to Capitol Hill." However, it looks like most of the rest of the world will begin the phase-out of HFCs, and a change in American leadership would likely see us back to joining the rest of the world in the fight to reduce climate-change impacts.
More efficient A/C units are the other part of dealing with the crisis. At current rates, thousands of new power plants would have to be built to accommodate the energy demand of the billions of new units people are going to want in the future. Each country will have to address this issue on its own, but local alternative-energy supplies could help, and as the Lawrence Berkeley Lab research points out, a 30 percent increase in efficiency could avoid the worst-case energy use situation.