> Climate change is a pretty simple proposal with pretty simple and direct evidence. Carbon traps light, which means more heat is trapped within the atmosphere. We can measure the amount of carbon in the atmosphere. That atmosphere will obey physics. More heat will be trapped.

Yes, but that's different from an apocalyptic scenario. Predicting the population increase in the 60s was also scientific. Predicting that we couldn't feed several billion people turned out to be wrong. Increased sea level rise and more extreme weather is one thing, predicting that human civilization ends and we all die is an entirely different matter.

Apcoalytic scenarios make worst case assumptions. That we'll fight a nuclear war which will trigger a nuclear winter, or that population won't peak and there's no green revolution, or that feedback loops will lead to a hothouse Earth scenario. But the likely projections don't show that.

It's funny that there is a set of people who think we can't survive +2 degrees of heat but can easily be an interplanetary species surviving in Mars.

I see no reason to suspect there's much overlap there, and in any case this misrepresents both arguments. Climate change doesn't need to render the planet uninhabitable to all life in order to devastate human civilization; if we are forced to abandon the coasts, it will be the biggest refugee crisis in human history by orders of magnitude, and hundreds of millions will die in the resulting chaos and scramble for resources. Meanwhile, Mars is a barren tomb world, and, at best, living in a colony there will be a physically and psychologically exhausting prospect, and has no chance at exhibiting any real self-sufficiency for hundreds of years at best, let alone anything resembling civilization.

Nobody thinks we can't survive 2 degrees of heat. After all typical climate fluctuations of more than 100 degrees are common in human experience. What you're describing is a strawman argument.

The actual concern is 2 degrees of average heat change and how that will change the web of systems that we rely on for current human civilization. Break enough subsystems in there and the human experience becomes dramatically different.