In the good old bad old days – tens of millions of years ago, deep time they call it – there were reptilian types strolling around the colder regions. Not because they had access to beautiful Cornelius furs and could rug up, grasshopper, but because the polar regions were little greenhouses back then.
Check out this article about ye olde climatic conditions, taken from an essay in the New Scientist, if I’m not mistaken, but you don’t have to subscribe to this one to read it. It’s very interesting, and a little scary. What more could you desire, my dears?