@scottearle @anon_opin It's the entire biosphere which is endangered. It's slightly misleading to say the planet was hotter/colder before, because while true, the difference in rate of change is orders of magnitude. To understand the full picture you need to look at a few hundred million years of geological timescale fluctuations in the carbonate-silicate cycle, and how it relates to the sequestered carbon in fossil fuels which we are now releasing all at once on a human generational timescale.