Global warming is happening, but it's not all mans fault.
Think about it, there have been Ice Ages every like 10k years or so. What causes them? A disruption in the oceanic currents, caused by warming. We are still on the warmup period between ice ages. Sure we are accelerating the warming a little, but that just means it's gunna get cold that much quicker. A good example would be the movie The Day after Tomorrow, and as unrealistic as it may seem that movie was based on fact. And no, I don't get my theories from movies...I had this one long before that movie came out. Discovery channel plus bordom-inspired research online
There is almost no chance at all that mankind's addiction to burning crap will be the end of the earth... The planet has repaired itself from much worse scenarios before (the meteor that took out the Dinosaurs comes to mind).
Give it 250 years, and there will be a Glacier going 1/3 the way up the Sears Tower. That's my only worry with global warming, the more we burn the sooner that will happen.