Yes, it happened before. It's fairly clear to me that global warming is 1) real and 2) part of a natural climate cycle. The anti-development blame capitalism approach the the phenomenon is exactly the wrong one: we'll want as well developed an economy as possible so we can survive not just as a species but as a free and prosperous society if the glaciers come south again. (Last time they made it to Nebraska).
Incidentally, I like your screen name: my daughter named her car 'Tim' because if you point at things (in it) they explode.