This is backward. If anything, it was a cooling climate that played a part, specifically the Ice Age which concentrated the large animals near coastal areas preventing them from migrating away from the hunting pressure.
In fact, the ice age + over-hunting theory appeared right here on FR not that long ago:
http://www.freerepublic.com/focus/f-news/1461424/posts
This, to me, suggests the author is trying to sneak in the global warming junk science into a story that really has nothing to do with warming.
As for the merrits of the introduction of these large anumals, every single instance of Man's tinkering around with introduction of outside species has brought disaster in one form or another. Witness the rabits to Australia, dogs and cats to New Zealand, Buffo frogs to Hawaii, etc.
Left unsaid is who's land they propose to take for their grand expiriment.
Heck, the author's trying to sneak global warming junk science into zoological and geological junk science, to at least he's consistant.
You'll notice that ya never see stories about Carter visiting Australia. Cause and effect!