In either case, the math is punishing. To stay under 2°C, global emissions would have to fall nearly to zero within the next several decades. To stave off 1.5°C, they’d have to drop most of the way toward zero within a single decade. This would entail, for starters: revamping agricultural systems, transforming manufacturing, scrapping gasoline- and diesel-powered vehicles, and replacing most of the world’s power plants.
