The IPCC reports say we might reach 4C, 5C or even more; based on the historical record, such a major change in such a short time - several orders of magnitude faster than previous CO2e-gases-linked mass extinction events - likely cannot be adapted to by the majority of species (there will of course also be a few evolutionary winners), resulting in potential extinction. I also quote the latest draft report from that same IPCC, leaked about two years back by concerned involved scientists to newspapers before the usual step where political stakeholders are allowed to reword the parts they deem too disturbing or against their interests:
"Life on Earth can recover from a drastic climate shift by evolving into new species and creating new ecosystems," it says. "Humans cannot."