Let’s pretend that the US didn’t recently pull out of the Paris Climate Agreement. Let’s also pretend that all the other countries that scolded it for withdrawing also met their Paris pledges on deadline. Heck, let’s pretend that that everyone in the whole world did their very best to cut emissions, starting today. Even if all that make-believing came true, the world would still get very hot.
Fact is, if you add up all the emissions cuts every country promised in their Paris pledges, it still wouldn’t keep the planet’s temperature from rising beyond the agreement’s goals—to keep global temperatures from rising more than 2˚ C higher than they were before the Industrial Revolution, and as close to 1.5˚ C as possible. If Earthlings want to avoid a heat-soaked, tide-swamped, and war-clouded future, they need to do more. This raises the specter of geoengineering: things like seeding the stratosphere with sulfur, or using ice crystals to dissolve heat-trapping clouds. But geoengineering is a dirty word many climate scientists and climate policy experts avoid, because humans meddling with nature doesn’t have the best track record. Which is why they say world leaders need to come up with some rules about geoengineering ASAP, before desperation over the coming climate catastrophe forces humanity to do something it might well regret.
But the technical challenges of geoengineering are minimal compared to the challenges governments face in deciding when, if, and how to deploy these technologies. The biggest worry of all is that some desperate country, or group of countries, might decide to do some geoengineering all on their own.