I have long known about global warming and the denial of some of it's existence. Last night I watched NOVA and learned about Global Dimming, a concept I had never even heard of before. It seems that particles of pollution are reducing the sun's heating of the earth masking the effect of the greenhouse gases. This is alarming material, except for those who deny all things scientific.
http://www.pbs.org/wgbh/nova/sun/
The lesson is don't f**k with Mother Nature, if you do, expect a mass extinction.