Well, we could still mitigate the consequences.
Once the heat buildup is an undeniable reality, we could still shade the earth partially from the sun’s energy, using an orbiting barrier. The ideal resource will be self-evident – the millions of people who have fought against climate science and its implications, who we refer to as “deniers.”
An individual denier’s body won’t cast a very big shadow, of course, but if we get enough of them into high, stationary orbits, the project should work – and the social justice benefits are obvious.