I don't see how you can compare communism, religious beliefs and socialism with AGW.
Governments don't believe in AGW the way people believe in god or jesus or some political idealogy. They believe it on advice of the scientific community.
"No scientific body of national or international standing has maintained a dissenting opinion [on AGW]; the last was the American Association of Petroleum Geologists, which in 2007 updated its 1999 statement rejecting the likelihood of human influence on recent climate with its current non-committal position.[10][11] Some other organizations, primarily those focusing on geology, also hold non-committal positions. Disputes over the key scientific facts of global warming are now more prevalent in the popular media than in the scientific literature, where such issues are treated as resolved, and more in the United States than globally."
Now which of the above schools of thought do you subscribe to? Scientific associations around the world or popular media and the Americans?
