More importantly, we should ask, should we? If the worst outcome is 3ft rise in sea level in 100 years, what’s the point of spending $50t+?

I agree with that this is possible. Fixing our planet is a technical problem that is strongly correlated with fixing other things we need (water, food, energy). Basically getting rid of fossil fuels is part of the solution. The tech for that already exists and many countries are pretty far done with the transition to clean energy sources. This will probably take a few more decades but at this point it's more a question of when rather than if this will go to it's ultimate conclusion of completely eliminating the use of fossil fuels for energy production.

In that same time frame most cars will be electric. There are also signs that ships and planes will be running on a combination of fuel cells and batteries in the next few decades as well. So, basically the entire transport and energy sector are in the process of cleaning up their act and progress is very rapid there; driven by cost and other advantages.

The next issue is fixing agriculture. We've turned quite a bit of land into desert the last century. Turning that around is going to require a bit of out of the box thinking but it is not impossible. Apparently soil can capture a lot of carbon, which gets released when the land dries out. So the existing practices of abusing the land with mono culture crops is very destructive. User of fertilizers and pesticides kills the soil. Plowing and burning kill it further. Wind and rain erodes soil that has nothing growing on it. That's the recent history of a lot of newly created desert.

So, fixing this would be a big deal and there are some people who are arguing this is a reversible process. Doing so, would produce usable farm land in the and turn currently useless land back into productive land. And if you consider planned grazing as part of the solution (some people do), that would fix a sustainable source of meat as well.

So, there's reason to be optimistic. I do feel the incentives are wrong, all of the above is happening because it is more economical. Being cleaner is a useful side-effect but we should drive home the point that it is more economical. Making clean the obvious economical choice is the key to speeding this up. Subsidize good things, tax bad things, put a stop to bad practices. Some countries are still getting this quite wrong by doing the opposite.

> does not apply here

It does. Because culling the human population by, say 50% in one step, would that lead to positive or negative effects in the context of climate change, ecosystems and overpopulation? Esp. if you choose the "right" half of people who are least essential for the global economy?

I disagree with using it as a descriptor, but the literal meaning of the word holocaust is something like "burning everything". So in the context of global warming it's actually weirdly applicable.

What are you talking about?? Mass extermination of life on Earth is genocide.

I'm worried about the tails. Recent revelations like the bug biomass loss should sober anybody up.

https://www.laboratoryequipment.com/news/2017/10/insect-biom...

Climate change could be a civilization-ending event. Even if the odds of catastrophe are low, say 10%, do you really want to bet the future of humanity on your assumption?

> migration off the coast

Do you have any idea what democracies are capable of becoming when faced with mass migration and resource shortage?