London: Water vapour in the atmosphere is
one of the major causes of global warming, climate scientists
have discovered, a finding which could help explain the
dramatic fluctuation in temperatures from decade to decade.
According to the study, published in the journal Science,
observations from weather balloons and satellites show that
"stratospheric water vapour" increased in the 1980s and 1990s
and dropped after 2000.
Dr Susan Solomon, of the US National Oceanic and
Atmospheric Administration, said: "Current climate models do a
remarkable job on water vapour near the surface.
Solomon said: "A 10 per cent drop in humidity 10 miles
above the Earth's surface explains why global temperatures
have been stable since the start of the century, despite the
rise in carbon dioxide in the atmosphere."
The study estimates that the drop in water vapour since
2000 caused surface temperatures to rise 25 per cent more
slowly than they would have done otherwise.
And the increase in stratospheric water vapour in the
1980s and 1990s is likely to have accelerated the rate of
global warming by around 30 per cent in the previous two
decades, the scientist said.
The findings do not challenge the theory of man-made
global warming, but the reasons why water vapour rises and
falls in the atmosphere still remain a mystery, the Daily Mail
reported.
PTI
First Published: Friday, January 29, 2010, 20:05