HFCs were once seen as a technological godsend. They were developed in response to the 1987 Montreal Protocol, a global agreement requiring nations and manufacturers to find a substitute for chlorofluorocarbons, or CFCs, then the dominant refrigerant, which was destroying the planet’s ozone layer. The chemical industry replaced that chemical with HFCs, which don’t harm the ozone layer but, as it turned out, added greatly to global warming.

The new agreement took seven years and required many determined advocates — major Western governments, the small island nation of Micronesia, poor African nations that fear drought and even starvation and persistent environmental groups. It was hardly a slam dunk. Despite obvious threats to their populations from rising sea levels and droughts, some developing countries like India pushed back hard, in part because their people were on the verge of being able to afford air-conditioners powered by HFCs.

The outcome was compromise — resulting, in part, from the last-minute efforts of Secretary of State John Kerry. The richest countries, including the United States, will freeze production and consumption of HFCs by 2018; much of the rest of the world, including China, Brazil and all of Africa, will do the same by 2024; and a few nations, including India, will have until 2028. Several newer and less harmful refrigerants are available, although they may be more expensive in the short run. The timetable will allow poorer countries to wait until prices come down. But unlike the Paris agreement, which consists of voluntary pledges, this one will be mandatory, with trade sanctions for nations that do not comply.

Countries have an enormous amount of work to do on all climate-changing pollutants, chiefly carbon dioxide. But the HFC agreement makes the job a little bit easier.