"0 BCE was way warmer than it is now. How modern do you need man to be?"
Humanity, not man. If 0 BCE was "way warmer" then it is now, the world population was also a tiny fraction of the current figures, urban centers were not dependent on a global web of food production and transport, local economies weren't interconnected to a global system, and humanity's response at the time to large scale environmental problems was typically to die in vast quantities. I personally don't want to approach environmental problems in the way they did in 0 BCE.