Does it honestly matter whether it is caused by man or not? Bottom line is, we are the only instrument on the planet that can change its' effects, and whether we or anything else are the cause, is that going to matter when global change affects crops and global political stability?

"A hungry man is an angry man"

If we need to leverage our present for our great grandchildren's futures, will it matter to them when we fail to act that it wasn't actually CAUSED by us..? If we COULD have fixed it but didn't?

BTW, according to this simple Google search, it isn't even POSSIBLE to determine CO2 levels during the dinosaurs age. About 20 million years is our limit, way past the 65 million year departure point of the terrible lizards. http://www.sciencedaily.com/releases/2009/10/091008152242.htm. And, according to this, to quote the article "The last time carbon dioxide levels were apparently as high as they are today — and were sustained at those levels — global temperatures were 5 to 10 degrees Fahrenheit higher than they are today, the sea level was approximately 75 to 120 feet higher than today, there was no permanent sea ice cap in the Arctic and very little ice on Antarctica and Greenland,"

But I bet that inconvenient fact didn't make it to 'Green Hell'.