LONDON (March 5) -- Climate scientists have hit back at skeptics with the
publication of a new paper that says the case for man-made global warming is now
"stronger than ever."
An international team of scientists led by
Britain's Met Office -- the country's national weather service -- has spent the
past year reviewing 110 studies published since 2007 that tracked changes in the
earth's climate. Their paper,
published in the journal Wiley
Interdisciplinary Reviews: Climate Change, concluded that the possibility
the world is warming because of natural variations in climate (such as increased
volcanic or solar activity) is "increasingly remote." Instead, they firmly pin
the blame on man's burning of fossil fuels.
"The science reveals a
consistent picture of global change that clearly bears the fingerprint of
man-made greenhouse gas emissions," said Peter Stott, head of climate monitoring
at the Met Office Hadley Centre for climate research. "Our climate is changing
now, and it's very likely human activity is to blame."
Public confidence in climate science has been knocked by a succession of
scandals over the past six months. Revelations that the 2007 report from the
U.N. Intergovernmental Panel on Climate
Change contained several unverifiable claims, and that the influential
climate unit at the University of East Anglia apparently withheld data from
skeptics, have led many people to doubt the theory of man-made climate
change.
Stott says the new Met Office report isn't an attempt to counter
this growing wave of skepticism, as the team started work a year ago, long
before those so-called Climategate scandals broke. But it is an unashamed
attempt to refocus the public debate on the actual science of climate change,
rather than claims made about individual scientists in the media. "I hope people
will look at that evidence and make up their minds informed by the scientific
evidence,"
he told the Guardian.
His team
put together the new set of evidence by comparing computer models of possible
causes of climate change, both human and natural, to actual measured changes in
air and sea temperature, Arctic sea ice cover, global rainfall patterns and
other factors. This forensic technique, known as "optimal detection," reveals
how much an observation can be explained by natural changes, such as volcanoes
or El Niņo, and how much it's attributable to atmospheric increases in carbon
dioxide and other greenhouse gases.
The study found that the climate
system had changed in ways that closely followed the pattern of man-made climate
change predicted by computer models. Human activity, it states, is almost
certainly the only explanation for climatic variations recorded across the world
-- such as the increase of rain in the northern countries and the decrease in
the south, or the retreat of Arctic sea ice.
Stott dismissed a popular
idea put forward by many skeptics that changes in the solar radiation (or
"global brightening") could be behind the shifts. "There hasn't been an increase
in solar output for the last 50 years," he said, "and solar output would not
have caused cooling of the higher atmosphere and the warming of the lower
atmosphere that we have seen."