Natural variation fits facts more closely.
International climate negotiations collapsed in December 2009 in Copenhagen (soon dubbed "Flopnhagen") - and the just-completed round in Cancun, Mexico, achieved little. Basically, the public no longer trusts the science being dispensed by the United Nations. Also, major developing countries, including China and India, refuse to sacrifice economic growth for an uncertain goal.
Yet, in most policy discussions- and in Al Gore's movie - it is still assumed, without question, that the warming trend, since about 1900, is human-caused. But there is no good evidence to support this belief except constant repetition of the mantra "The science is settled." The summary of the 2007 report of the U.N. Intergovernmental Panel on Climate Change (IPCC) claims as its key conclusion: "Most of the observed increase in global averaged temperatures since the mid-20th century is very likelydue to the observed increase in anthropogenic greenhouse gas concentrations." But the evidence they present is not at all convincing - and indeed, there is contrary evidence that the IPCC cavalierly ignores. The claimed reality of man-made or anthropogenic global warming (AGW) is of obvious importance and is key to any policy of climate mitigation.
A commonly cited "proof" for AGW claims there is a "scientific consensus" - based mainly on a flawed study by University of California science historian Naomi Oreskes, published in the journal Science in December 2004. However, a 2003 poll by German researchers of 530 climatologists in 27 countries showed just 34.7 percent endorsing the AGW hypothesis, while 20.5 percent rejected it - with the rest undecided. In a 2006 survey of 793 members by the National Registry of Environmental Professionals, 41 percent disagreed that recent warming "can be, in large part, attributed to human activity." There are statements from scientific groups and professional societies on both sides of the issue.