What are HFCs and what's their role in climate change?

Nations have agreed to cut back on a class of greenhouse gases called HFCs or hydrofluorocarbons, in a further step to reduce the effects of global climate change.

"If you have a car that is 1995 model or newer, chances are that inside the AC system there are HFCs pumping around keeping you cool," said Edward Parson, professor of environmental law at UCLA's Emmett Institute on Climate Change and the Environment. "They're also in your food store, refrigerated trucks, building chillers – they've grown rapidly since the 90s."

The deal, agreed to in Kigali, Rwanda on Saturday, cuts them by 85 percent for the richest countries, including the U.S., by 2036, said Parson. The timetable is different for developing countries. California has cited HFCs as key to reduce in order to reach its climate goals.

Though a step forward, the focus still needs to be on CO2, which makes up the bulk of greenhouse gas emissions in the atmosphere, said Parson.

"This is a real contribution and it avoids a real risk of things being even worse than they otherwise would have been," he said.