What about Milankovitch Cycles? It seems more plausible to me than man made global warming.
We've got this huge firey mass not so far away. At times, we get closer, and at times we get further.
This sphere of nuclear fusion is not regulated like these wonderful CFL bulbs we know are volunforced
to use. It's radiated power increses and diminishes, and it even wobbles in it's rotations.

We being here on earth recieve it's energy even when we are trying to save to polar bears.
We as the surface of the earth, being in it's radiation path absorb somewhere around
3.6490959132063×10 to the 18th power MBtu per year. The earth's total human energy
consumption is approximately 4.7390856015666×10 to the 14th MBtu per year. The rest
of it is reflected back up, and away to be absorbed, or consumed. How much have we changed
it with CO2, how much with asphalt roads, and massive cities? Could we warm it up intentionally,
not as much as a minor shift in our orbit. Could we cool it down? Not as much as a purge of volcanic ash.





The Earth gets hot, the Earth gets cool. Don't like? Stick around for a while,
It will change again(since the Younger Dryas stadial was a while back, anyone interested might want to grab a Snickers).