
Greenhouse theory smashed by biggest stone
Date: Monday, March 13, 2006 @ 20:41:08 UTC Topic: General
From: http://www.physorg.com/news11671.html
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
|
|