One of the unsettling aspects of the global warming debate is the way the some supporters of the hypothesis used data selectively to advance their cause. It is unclear whether there was actual dishonesty involved, or if is a matter of confirmation bias. Two factors involved in the global warming hypothesis are particularly troubling. First is the "Mann hockeystick" temperature history curve. There was a lot of discussion between people who believed in the global warming hypothesis of the need to "get rid" of the Medieval Warm Period. Then Mann did it with an approach that has been thoroughly discredited by McIntyre and McKitrick, and others. The second issue concerns the build-up of CO2 in the atmosphere where supporters of the hypothesis have taken control of the data, and have used data selectively to promote the idea that the atmospheric level of CO2 went up dramatically during the twentieth century. A significant amount of data, in fact, most of the data from the nineteenth century had to be rejected on the basis that it did not fit the pre-conceived notion of what should have been. Here is an article discussing the atmospheric CO2 question.

http://canadafreepress.com/index.php/article/6855