A controversial new theory attributes climate change not to atmospheric carbon dioxide levels but water vapor. In an unpublished paper, Vladimir Shaidurov of the Russian Academy of Sciences argues that the apparent rise in average global temperature recorded by scientists over the past hundred years could be due to atmospheric changes resulting from the Tunguska Event, a massive explosion over Siberia on the June 30th, 1908 that is thought to have resulted from an asteroid or comet entering the earth's atmosphere and exploding. Shaidurov says that the event could have caused "considerable stirring of the high layers of atmosphere" and triggered the subsequent rise in global temperatures.

According to Shaidurov's theory, "small changes in the atmospheric levels of water, in the form of vapour and ice crystals can contribute to significant changes to the temperature of the earth's surface, which far outweighs the effects of carbon dioxide and other gases released by human activities." Shaidurov claims that a 1 percent rise of water vapour could raise the global average temperature of Earth's surface by more than 4 degrees Celsius.

Shaidurov's argument will likely be met with skepticism by most atmospheric scientists who contend that human emissions of carbon dioxide and methane are primarily responsible for climbing temperatures since the beginning of Industrial Revolution. Earlier today, the National Oceanic and Atmospheric Administration (NOAA) released data showing that carbon dioxide levels reached 381 parts-per-million in 2005, the highest atmospheric concentration of the greenhouse gas in at least 650,000 years. The NOAA data comes on the heels of a NASA study that found 2005 was the warmest year in at least a century and research from the Alfred Wegener Institute for Polar and Marine Research which found a close correlation between atmospheric carbon dioxide levels and global temperatures.