First, I'd like to clear up the meaning of "global warming". Global warming is definitely occurring. The question is, is it mostly "natural global warming" or "anthropogenic global warming"? Now, global temperatures have varied a lot over human history. There were glaciers around the Great Lakes as recent ago as 5000 BC. The "Little Ice Age" caused all sorts of crop failures in Europe during the middle ages. Since the 19th century, the world has been getting warmer, but any number of things could be causing it.

Still, global warming is useful as a tool to get people to stop using such large amounts of fossil fuels, even if the risk is overstated. Eventually, we're going to run out, and unless we have a backup plan, we're going to be in a world of hurt when that happens. So, I work with the global warming people anyway, even if our reasons for doing what we do are different.