Global
Warming Fastest
For 20,000 Years
By Steve Connor
04 May 2006
The Independent
Global warming is made worse
by man-made pollution and the scale of the problem is unprecedented
in at least 20,000 years, according to a draft report by the world's
leading climate scientists.
The leaked assessment by
the group of international experts says there is now overwhelming evidence
to show that the Earth's climate is undergoing dramatic transformation
because of human activity.
A draft copy of the report
by a working group of the Intergovernmental Panel on Climate Change
(IPCC) states that concentrations of carbon dioxide, methane and other
greenhouse gases are at the highest for at least 650,000 years.
It predicts that global average
temperatures this century will rise by between 2C and 4.5C as a result
of the doubling of carbon dioxide levels caused by man-made emissions.
These temperatures could
increase by a further 1.5C as a result of "positive feedbacks"
in the climate resulting from the melting of sea ice, thawing permafrost
and the acidification of the oceans.
The draft report will become
the fourth assessment by the IPCC since it was established in 1988 and
was meant to be confidential until the final version is ready for publication
next year.
However, a copy of the report
has been made available by a US government committee and can be found
on the internet by anyone who makes an e-mail request for a password
to access the area on its website.
The US Climate Change Science
Programme, which yesterday released its own report saying climate change
was being affected by man-made pollution, said it wanted as many experts
and stakeholders as possible to comment on the draft IPCC report.
The IPCC's chairman, Rajendra
Pachauri, however, did not learn of the decision to, in effect, publish
the report until it was posted online, according to the journal Nature.
The IPCC assessment is written by scores of scientists - who can draw
on the expertise of hundreds more researchers - to produce the most
definitive and authoritative assessment of climate change and its impacts.
Global warming sceptics will
get little comfort from the confident language in the draft report,
which dismisses suggestions that climate change is an entirely natural
rather than man-made phenomenon.
"There is widespread
evidence of anthropogenic warming of the climate system in temperature
observations taken at the surface, in the free atmosphere and in the
oceans," it says.
"It is very likely that
greenhouse gas forcing has been the dominant cause of the observed global
warming over the past 50 years.
"And it is likely that
greenhouse gases alone would have caused more warming than has been
observed during this period, with some warming offset by cooling from
natural and other anthropogenic factors." Since its last report
in 2001, the IPCC's working group says it has amassed convincing evidence
showing that climate change is already happening.
It also finds that climate
change is set to continue for decades and perhaps centuries to come
even if man-made emissions can be curbed.
"2005 and 1998 were
the warmest two years on record. Five of the six warmest years have
occurred in the past five years (2001-2005)," the report says.
Satellite data since 1978
shows that the Arctic sea ice has shrunk by about 2.7 per cent each
decade, with even larger losses of about 7.4 per cent during the warmer
summer months.
"The smallest extent
of summer sea ice was observed in 2005. Average Arctic temperatures
have been rising since the 1960s and 2005 was the warmest Arctic year,"
the draft IPCC report says.
"An increasing body
of evidence suggests a discernible human influence on other aspects
of climate, including sea ice, heat waves and other extremes, circulation,
storm tracks and precipitation," it says.
Melting glaciers and polar
ice sheets could cause sea levels to rise by up to 43cm by 2100, and
the rise for the next two centuries is predicted to be nearly double
that figure.
Man-made emissions of greenhouse
gases have probably already caused the increase in sea levels observed
over the past century, says the report.
"Anthropogenic forcing,
resulting from thermal expansion from ocean warming and glacier and
ice sheet melt, is likely the largest contributor to sea level rise
during the latter half of the 20th century," the report says.
"Anthropogenic forcing
has likely contributed to recent decreases in Arctic sea ice extent.
There is evidence of a decreasing trend in global snow cover and widespread
retreat of glaciers consistent with warming and evidence that this melting
has also contributed to sea-level rise," it adds.
Evidence of climate
change
* Arctic sea ice has shrunk
by 2.7 per cent per decade since 1978 and by 7.4 per cent each decade
during the summer months.
* Five of the six warmest
years have occurred in the past five years, with 2005 and 1998 being
the two warmest years on record.
* Global average sea levels
rose at a rate of about 2mm a year between 1961-2003, and by an average
of more than 3mm a year between 1993-2003.
* Mountain glaciers and polar
land ice have in general melted faster than they have formed over the
past 40 years.
* Permafrost temperatures
have increased on average and the area covered by seasonally frozen
ground has decreased by about 7 per cent over the past 50 years.
© 2006 Independent News
and Media Limited