It's increasingly likely that at some point, the world's nations will need to broach the fraught discussion of geoengineering. The UN climate accord was a natural forum to do it.
Yes, we blunt the effects of climate change by getting off fossil fuels. But countries' most ambitious targets imply use of climate engineering schemes – and that discussion should be done in public.
Blocking the sun by injecting tiny particles in the atmosphere – called solar geoengineering – can lower the Earth's temperature but has some real costs. Economists run the numbers.