He noted that the force of the blast was about that of 10-15 million tons of TNT and that an atmospheric shock wave circled the globe twice. Fine dust permeated the atmosphere sufficiently that “...for two days afterwards, there was so much fine dust in the atmosphere that newspapers could be read at night by scattered light in the streets of London, 10,000 km (6,213 miles) away.”
A Russian scientist believes that the Tunguska Event was responsible for global warming rather than man-made gases. Vladimir Shaidurov, of the Russian Academy of Sciences, theorizes that water vapor thrown into the earth's meteorological system is the cause of present climatological change. “Andrew E. Dessler of the Texas A & M University, writing in The Science and Politics of Global Climate Change, claims that: "Human activities do not control all greenhouse gases, as the most powerful greenhouse gas in the atmosphere is water vapor. 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."
The English version of Pravda on-line recently offered the theory again that it was caused by a UFO. It is not a very compelling theory but the fact that there is an English version of Pravda and that it reads like a super-market tabloid was a fascinating aside in this research.
The NASA/JPL photo of Asteroid 243, Ida and Dactyl (Asteroid and her satellite) was shot by the Galileo spacecraft in 1993 on its way to Jupiter at 10,500 km (6500 miles) from the pair.
In 2002 Earth had a “close shave.” Asteroid 2002MN became one of only 6 recorded asteroids to penetrate within the orbit of the moon. Astronomically that is surprisingly close. Especially since it was only discovered 3 hours after its closest shave with a defenseless planet. It came within 12,000 km (7,457 miles) which is 0.0008 astronomical units (distance from Earth to Sun). If it had hit it would have been as powerful as Tunguska – equal to a few H-bombs and it was too small to be in the group that we are to be planning defenses against.