 The Roman warm period around the time of Christ saw huge amounts of growth. The medieval warm period around 900 to 1200 AD also saw huge amounts of growth. So humans do better in a warmer climate. And I will say this, there was a study in the Lancet, the most respected medical journal on the planet, a couple of years ago that showed distinctly that there are more deaths associated with cold temperatures than warm temperatures by about a factor of 10.