[meteorite-list] New Theory: Global Warming Caused by Tunguska Event

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Mar 14 10:31:00 2006
Message-ID: <200603131753.k2DHrs514090_at_zagami.jpl.nasa.gov>

http://www.physorg.com/news11671.html

Greenhouse theory smashed by biggest stone
Space and Earth Science
March 13, 2006

A new theory to explain global warming was revealed at a meeting at the
University of Leicester (UK) and is being considered for publication in
the journal "Science First Hand". The controversial theory has nothing
to do with burning fossil fuels and atmospheric carbon dioxide levels.
According to Vladimir Shaidurov of the Russian Academy of Sciences, the
apparent rise in average global temperature recorded by scientists over
the last hundred years or so could be due to atmospheric changes that
are not connected to human emissions of carbon dioxide from the burning
of natural gas and oil.

Shaidurov explained how changes in the amount of ice crystals at high
altitude could damage the layer of thin, high altitude clouds found in
the mesosphere that reduce the amount of warming solar radiation
reaching the earth's surface.

Shaidurov has used a detailed analysis of the mean temperature change by
year for the last 140 years and explains that there was a slight
decrease in temperature until the early twentieth century. This flies in
the face of current global warming theories that blame a rise in
temperature on rising carbon dioxide emissions since the start of the
industrial revolution. Shaidurov, however, suggests that the rise, which
began between 1906 and 1909, could have had a very different cause,
which he believes was the massive Tunguska Event, which rocked a remote
part of Siberia, northwest of Lake Baikal on the 30th June 1908.

The Tunguska Event, sometimes known as the Tungus Meteorite is thought
to have resulted from an asteroid or comet entering the earth's
atmosphere and exploding. The event released as much energy as fifteen
one-megaton atomic bombs. As well as blasting an enormous amount of dust
into the atmosphere, felling 60 million trees over an area of more than
2000 square kilometres. Shaidurov suggests that this explosion would
have caused "considerable stirring of the high layers of atmosphere and
change its structure." Such meteoric disruption was the trigger for the
subsequent rise in global temperatures.

Global warming is thought to be caused by the "greenhouse effect".
Energy from the sun reaches the earth's surface and warms it, without
the greenhouse effect most of this energy is then lost as the heat
radiates back into space. However, the presence of so-called greenhouse
gases at high altitude absorb much of this energy and then radiate a
proportion back towards the earth's surface. Causing temperatures to rise.

Many natural gases and some of those released by conventional power
stations, vehicle and aircraft exhausts act as greenhouse gases. Carbon
dioxide, natural gas, or methane, and chlorofluorocarbons (CFCs) are all
potent greenhouse gases. Carbon dioxide and methane are found naturally
in the atmosphere, but it is the gradual rise in levels of these gases
since the industrial revolution, and in particular the beginning of the
twentieth century, that scientists have blamed for the gradual rise in
recorded global temperature. Attempts to reverse global warming, such as
the Kyoto Protocol, have centred on controlling and even reducing CO2
emissions.

However, the most potent greenhouse gas is water, explains Shaidurov and
it is this compound on which his study focuses. According to Shaidurov,
only 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. Just a rise
of 1% of water vapour could raise the global average temperature of
Earth's surface more then 4 degrees Celsius.

The role of water vapour in controlling our planet's temperature was
hinted at almost 150 years ago by Irish scientist John Tyndall. Tyndall,
who also provided an explanation as to why the sky is blue, explained
the problem: "The strongest radiant heat absorber, is the most important
gas controlling Earth's temperature. Without water vapour, he wrote, the
Earth's surface would be 'held fast in the iron grip of frost'." Thin
clouds at high altitude allow sunlight to reach the earth's surface, but
reflect back radiated heat, acting as an insulating greenhouse layer.

Water vapour levels are even less within our control than CO2 levels.
According to Andrew E. Dessler of the Texas A & M University writing 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, he says, "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."

As such, Shaidurov has concluded that only an enormous natural
phenomenon, such as an asteroid or comet impact or airburst, could
seriously disturb atmospheric water levels, destroying persistent
so-called 'silver', or noctilucent, clouds composed of ice crystals in
the high altitude mesosphere (50 to 85km). The Tunguska Event was just
such an event, and coincides with the period of time during which global
temperatures appear to have been rising the most steadily - the
twentieth century. There are many hypothetical mechanisms of how this
mesosphere catastrophe might have occurred, and future research is
needed to provide a definitive answer.

Source: University of Leicester
Received on Mon 13 Mar 2006 12:53:54 PM PST