Global warming is man effected nomatter how you put it. Its completely out of its natural cycle. And thats the reason next year ships will start to sail over the north pole from Europe to China/Korea/Japan and cut about 25 days of sailing of.
Ice drilled cores dating 100 of thousand years back can tell you that. Plus its not really complicated for most people to see its a runaway greenhouse situation.
Or maybe you wish us to end like Venus?
First the worst predictions of the northpole being ice free was 2070. Then 2050. Now we might have it in 2010.
This is the northpole september 2008:
http://i2-images.tv2.dk/s/74/1046337...0efe7e2c8.jpeg
Compared to earlier:
http://upload.wikimedia.org/wikipedi...ic_Sea_Ice.jpg
Its abit like playing russian roulette to do nothing.