The proponents of global warming don't actually know that the earth is warming, though they think it is based on faith rather than science. They actually are more interested in politics and science, and use science to achieve political aims. They deliberately obfuscate the data and analyses that they assert 'prove' that CO2 emissions are destroying the climate of Earth. That is why they consistently refuse to debate the issue with people who are knowledgeable about the subject, hiding behind an assertion that 'the science is settled.' Their attitude should make any open-minded person suspicious. Here is an article that discusses the validity that the Bush Administration tried to silence James Hansen, something that clearly did not happen despite Hansen's claims. There is also information on the relationship between Hansen and Obama.

http://www.cheatseekingmissiles.com/2009/01/30/the-hansen-slap-down/