Warm weather spurs evolution. Its why bacteria grow faster at room or warm temps. The more faster they grow, the faster they divide. The faster they divide, the more traits gain or lost. Its why rainforests have the most diversity on land. Wet, humid and warm.

Ecosystems shift all the time. Sahara used to be rainforest and used to be grassy plains, but became desert way before humans came about. Antartica used to be aboreal forests before tectonics moved it south. Basically... climates shift all the time. Some miniscule humans burning coal and gas for 100 years aint gonna do shit to climate. Timescale is just too short. Maybe 10,000 years would cause things to be bad.. but yeah.