This idea that global warming is caused primarily by humans is speculative at best. In the past 120 years, the average surface temperature has only risen 1.2 degrees F in North America. Because measuring has not been as accurate as it is now, this may not be a totally accurate number. Plus, most of this can be attributed to things not caused by human action such as retreated glaciers, volcanos, etc. Do we really know for sure that WE are causing global warming?
Also, think of all the negatives of fighting this perceivedly harmful warming. One, the poor will become poorer because they won't be able to afford the latest fuel efficient cars, furnaces, etc. We just recently purchased a "new" (used) car and found that it was manufactured to meet california emissions standards, though we do not live in California nor was it manufactured there. Because of this, a simple $50 oxygen sensor that needs replacing is now going to cost $150. On top of that, it has not 1 but 2 catalytic converters, which are another expensive part to replace. Then think about the benefits of global warming. Warmer weather means a longer growing season, which could be a boon to agritculture in 3rd world countries. Also, more people die from cold each year than from heat, so a warmer planet could mean less deaths due to temperature.
Of course, these are assuming the warming doesn't eventually result in some sort of catastrophe, but I think the evidence for this is very shaky at best. Don't believe everything the media is spitting out currently. I think this whole catastrophe theory is a very politically motivated issue with a little bit of science behind it.