For you global warming fear-mongers out there, here is something to REALLY worry about: Asteroids.
What we know about the effect of greenhouse gases on the Earth is nothing compared to what we know about asteroids.
Asteroids have hit the Earth before, possibly having wiped out the dinosaurs.
Unless there is a miracle, we WILL get hit by a large asteroid again.
We are doing more to limit greenhouse gases than we are doing to prevent an asteroid from hitting the Earth.
Of course, denial is a wonderful thing. You can keep believing that humanity can control the Earth's atmosphere (which we can't), while living in denial about the possibility of the Earth being hit by an asteroid, about which we COULD actually do something.