http://www.planetark.com/dailynewsstory.cfm/newsid/43042/story.htm
Solar Variations Not Behind Global Warming - Study
UK: July 11, 2007
LONDON - The sun's changing energy levels are not to blame for recent
global warming and, if anything, solar variations over the past 20
years should have had a cooling effect, scientists said on Wednesday.
Their findings add to a growing body of evidence that human activity,
not natural causes, lies behind rising average world temperatures,
which are expected to reach their second highest level this year since
records began in the 1860s.
There is little doubt that solar variability has influenced the
Earth's climate in the past and may well have been a factor in the
first half of the last century, but British and Swiss researchers said
it could not explain recent warming.
"Over the past 20 years, all the trends in the sun that could have had
an influence on Earth's climate have been in the opposite direction to
that required to explain the observed rise in global mean
temperatures," they wrote in the Proceedings of the Royal Society.
Most scientists say emissions of greenhouse gases, mainly from burning
fossil fuels in power plants, factories and cars, are the prime cause
of the current warming trend.
A dwindling group pins the blame on natural variations in the climate
system, or a gradual rise in the sun's energy output.
In order to unpick that possible link, Mike Lockwood of Britain's
Rutherford Appleton Laboratory and Claus Froehlich of the World
Radiation Centre in Davos, Switzerland, studied factors that could
have forced climate change in recent decades, including variations in
total solar irradiance and cosmic rays.
The data was smoothed to take account of the 11-year sunspot cycle,
which affects the amount of heat the sun emits but does not impact the
Earth's surface air temperature, due to the way the oceans absorb and
retain heat.
They concluded that the rapid rise in global mean temperatures seen
since the late 1980s could not be ascribed to solar variability,
whatever mechanism was invoked.
Britain's Royal Society -- one of the world's oldest scientific
academies, founded in 1660 -- said the new research was an important
rebuff to climate change sceptics.
"At present there is a small minority which is seeking to deliberately
confuse the public on the causes of climate change. They are often
misrepresenting the science, when the reality is that the evidence is
getting stronger every day," it said in a statement.
The 10 warmest years in the past 150 years have all been since 1990
and a United Nations climate panel, drawing on the work of 2,500
scientists, said this year it was "very likely" human activities were
the main cause.
The panel gave a "best estimate" that temperatures would rise 1.8 to
4.0 degrees Celsius (3.2 to 7.8 Fahrenheit) this century.
Story by Ben Hirschler
REUTERS NEWS SERVICE
posted to ClimateConcern
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