2. We know that the earth has been substantially warmer in the past (with accompanyingly higher CO2 levels) and life thrived Nobody is worried that all life on

2. We know that the earth has been substantially warmer in the past (with accompanyingly higher CO2 levels) and life thrived Nobody is worried that all life on Earth will end for good. We're worried it's going to be a pretty miserable place for humans to live, and that it will take a couple million years for diversity to return. Life can handle +10F (silver bullet ants anyone?), but humans have a temperature limit.