Many Western nations have substantially reduced their emissions already. This did not result in catastrophic reductions in living standards. And these reductions happened before the current exponential cost improvements in renewables really began to cross the “knee”. At the same time there are fossil fuel interests and politicians who are trying to slow down renewables and promote more fossil drilling, even when it’s not economic. (And China is burning massive amounts of coal for reasons that make less economic sense every month.) This stuff is “set the controls for the heart of the sun” levels of suicidal. We won’t survive it.

As for geoengineering, good luck. While I also think this may be necessary, a precondition for spraying stuff into the sky is convincing people that this kind of intervention is necessary. Good luck doing that while enormous financial interests are trying to convince the world that it’s safe to keep digging up and burning fossil fuel deposits. They may not object to geoengineering itself, but they can’t afford to permit the kind of consensus it would require to get geonengineering done, so they will throw resources at fighting that consensus until it’s too late.

Option D is hoping the mass social unrest will cause enough (of the right) people to die off or actively steering towards that. A final solution one might say.

Option D: less people by any means necessary.