The most significant part of the bill for the rapidly overheating planet is a requirement for U.S. companies to cut production and use of hydrofluorocarbons, or HFCs, by 85 percent over the next 15 years. HFCs — which are commonly used in refrigerators and air-conditioning systems — were supposed to be a safe alternative to chlorofluorocarbons, the chemicals that deplete the ozone layer. But scientists discovered that when released into the atmosphere, HFCs are 1000 to 3000 times more effective than carbon dioxide at trapping heat. They are now the fastest-growing greenhouse gas in the world.

HFCs are regulated internationally by the Kigali Amendment, a 2016 update of the ozone-protecting Montreal Protocol, which was enacted in the late-1980s. Although over 100 nations have ratified the amendment — thus promising to cut global HFC emissions 80 percent or more by 2050 — the big emitters like the U.S., China, and India haven’t yet signed onto the effort.