This is why the climate change discussion is so obnoxious. They present these comparative static analyses (other things equal), to freak people out, that obviously leave out so many other relevant factors that also change.

For instance, reptiles live in the warmer parts of the Earth, with much of the land mass being too cold for them. As temperatures warm, their habitable area increases and their food supply increases, so their populations actually increase. That's why, when the Earth was much warmer than it is today, every single ecosystem was dominated by reptiles.

If you actually think scientifically, you can ask yourself if their hypotheses withstand the scrutiny of the evidence we already have.