By Adele Peters

The world’s carbon budget—the amount of greenhouse gas emissions that humans can still pump into the atmosphere before we no longer have a chance of keeping global warming at 1.5 degrees Celsius—is almost used up.

In a landmark report last year, the UN’s climate body, the IPCC, said that we need to essentially halve emissions by 2030 to have a 50% chance of staying under 1.5 degrees. That deadline is now only about 10 years away. But the actual situation is even more urgent because of the problem of “committed emissions,” all of the cars and power plants and furnaces and other things that already exist now and have years or decades left of use.