Here's the data presented by the left as "evidence" of Man's climatic misdeeds...
Looks pretty nasty, huh? Things are going swimmingly until the GOP takes power with TR. It must be their fault, right? But there's a problem with this graph. It isn't graphing global temperature; it's graphing tree ring data. (And only for part of the northern hemisphere.) What tree ring data alone fails to show is temperature variations we know existed in the past...
One can argue with what the exact temperature was during the "Little Ice Age", but we do know that it happened. This plot shows it, but the "hockey stick" above does not. Nor does it show the Medieval Warm Period we know preceded the LIA. Other proxies must be used along with tree ring data to show what the earth's surface was doing. And while temperatures are higher than they were during the 19th Century, they are not as warm as they were during the 11th-14th Centuries.
"Global Warming" is a myth. It is built upon pseudoscience. It's aim, as you point out, is the accumulation of political power by the left. Bush is helping the left put that plan into action by allowing the EPA to continue this faerie tale.