Re: Here is a different take on global warming
- From: "Carsten Troelsgaard" <carsten.troelsgaardNOSPAM@xxxxxxx>
- Date: Tue, 14 Mar 2006 10:57:40 +0100
"George" <george@xxxxxxxxxxxxxxxxxxxxx> skrev i en meddelelse
news:wltRf.860080$xm3.673560@xxxxxxxxxxxx
Don't shoot the messenger. I'm just posting it. I didn't write it.
George
http://www.eurekalert.org/pub_releases/2006-03/uol-gts031306.php
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.
This must be an error. Thin clouds at high altitutes would heighten the
albedo.
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.
I don't recall to have met any suggestions as to the material nature of the
Tunguska meteorite ... would it make sense for something to explode without
leaving some material behind even though some or most of it would sort of
scate off the atmosphere and return to space? I suppose the author may solve
two questions by his suggestion, the nature of the meteorite (ice) and
climatic change? ... This suggestion may hold until the heat of the 'vapour'
disperses and the vapour turn into water or ice (unless nucleation is
impeded)
Carsten
.
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