I wrote a term paper on global warming once. Really didn't prove anything either way, BUT:
At least once in the past, the average temp on Earth was some 14 degrees warmer than it is now. And scientists are freaked out because it warmed a degree or so in the last century.
Then, take the Earth as a whole, subtract the 71% that is under water. Subtract the polar regions, subtract the uninhabited/uninhabitable areas, subtract the undeveloped countries that produce no emissions, subtract the agricultural areas, and subtract the wilderness ares. (The U.S. is 38% wilderness).
The area you have left where man MAY engage in activities that can affect climate and global temperature is really quite small.