Here is a video on Global Warming prepared by Canadians. Al Gore wouldn't like this. One of the things proponents of man as the cause of climate change have done is to try to eliminate the Medieval Warming Period, and to imply that climate has been more or less constant throughout the time man has been on Earth. That was discussed widely among the proponents before the famous Mann Hockey Stick graph was published. (Our Arlington, Texas Congressman, Joe Barton, forced Mann to release the data and statistical analysis that was the basis for the graph; subsequently the graph has been debunked. Barton has been reviled for forcing Mann to release his notes. One of the curious things about the science behind the theory that man is causing irreversible climate change is that the basis won't be given out for independent researchers to evaluate. A scientific theory that is not duplicated by independent researchers is not proven. Actually man as the cause of climate change is not a scientific theory at all; it is the output of computer simulations that attempt to model the Earth's ecosystem.) Another thing that I have noticed is that proponents never mention that water vapor is the primary greenhouse gas, that clouds have an important impact on Earth's temperature, and that the models do not do a good job of predicting cloud action. If you haven't seen it, take a look at the Canadian video; it is 25 minutes in length.

http://video.google.com/videoplay?docid=-4468713209160533271&hl=en