That book was The Ministry for the Future (2020) by Kim Stanley Robinson and the solution involved assassinations at scale of oil and gas industry executives as well as destruction by drone of all fossil fuel tankers and egregiously polluting cargo ships. Also, massive releases of sulfur dioxide into the atmosphere, aggressive immobilization of Antarctic glaciers via water pumps, and the onboarding of all central banks to rebase currency according to how much CO₂ you can fix into the ground instead of capitalism's belief in endless future growth. It is a very optimistic story, but one we'll have to carry out eventually in some form to at least the degree described in the book.

That was a surprisingly grisly start to an otherwise extremely disappointing book.