Increase in temperature could actually increase agricultural output long term. Melting ice in Greenland and in Antarctica could provide the fresh water. Also, there's no fundamental reason why human population should increase indefinitely. Perhaps it will stabilize to an environmentally sustainable level. By the way Pangaea was mostly a desert due to it's smaller ratio of shoreline length to landmass. My main point is that I don't know which way is "better": global warming could be bad, or it could actually be good, or overall irrelevant (bad in some places, good in others). I do not know if anybody actually knows this.
Not to mention when will the change stop? There isn't any indication it will stabilize in the near future meaning semi-unpredictable changes will continue to occur.
Also, living through the snowball earth era would have probably been awful for the human species. Sure life survived many apocalyptic events, no reason to think our species would survive when 99% of others couldn't.