It is true that the earth has already been warmer. We're reaching points that humans are never seen, though.

Second, the problem here is not only the total temperature variation but the speed at which the temperature is changing.

Think of the difference between a car going from 130 km/h to 0 km/h in 8 seconds, and a car going from 130 km/h to 0 km/h in 0.3 seconds. Not really endearing.

Understood, although we have no way to know if there have ever been similar events, as the geologic record is something of a low-pass filter.

Just for the sake of argument, let's say you find yourself in a car in the second scenario, with no known way to stop it. What would you do? I say this as a pragmatist - if we take the headlines at face value, and we only have ~10 years to avert a catastrophe, then the only realistic way to avert it is if 90% of the world's population spends that 10 years planting trees before killing themselves.

I'm not sure what the point of suicide is when the worst that can happen as a result of climate change is death.

Right, so what should we do?