Tunguska Event

Shaidurov explains that the levels of carbon dioxide and methane, the other two greenhouse gases are not the cause behind global warming but the effect of global warming. That this might be so has long been speculated, because global warming seems to have preceded the increase in carbon dioxide and methane. But Shaidurov also explains the mechanism:

"The point is that the average increase of land and ocean temperature produces higher average absolute humidity. In its turn, this raises the assimilation ability of the atmosphere even at constant content of carbon dioxide. But increasing the average ocean temperature is responsible for lower water solubility of carbon dioxide, which then arrives in the atmosphere. Moreover, increase in land temperature is responsible for growth of bogs, at least in Northern Russia, due to the removal of permafrost deep down. The rise in area and activity of bogs leads to more active production of methane. Thus, a self-stimulated process was launched for the increase of average temperature of the Earth's surface. Therefore the rise of greenhouse gas concentration is more a consequence of warming but not a main reason."

Therefore, there exists a positive feedback mechanism at work: the Tunguska Event has changed the distribution of water vapors and ice crystals in the atmosphere (the nature of the clouds) and has started the global warming; global warming produces an increase in the levels of the other greenhouse gases such as carbon dioxide and methane, and these in turn also contribute to the increase in global warming. However, the CO2 and the methane are negligible compared to the water vapors. A rise of just 1% of water vapor could raise the global average temperature of Earth's surface more then 4 degrees Celsius.

As Andrew E. Dessler of the Texas A & M University writes in 'The Science and Politics of Global Climate Change': "Human activities do not control all greenhouse gases, however. The most powerful greenhouse gas in the atmosphere is water vapour. Human activities have little direct control over its atmospheric abundance, which is controlled instead by the worldwide balance between evaporation from the oceans and precipitation."