Animal and plant life have always thrived during times of high CO2 levels and warm climates. Lush tropical climates are perfect for life. It's only when climates turn cold & dry, that life struggles to survive. 'Global Warming' will not spell the end of humanity. In fact, humanity will likely thrive.
Actually if you look at say, the great empires, what we see is a decline when things get too hot.
The Egyptians were followed by the Greeks and then the Romans. As things changed so too did the areas able to sustain great empires.
Are equatorial countries at the top of the GDP pile? No, in fact it is mostly countries in milder climates, Europe, China, Japan, North America, etc.