The
Earth Today Stands In
Imminent Peril
By Steve Connor
19 June, 2007
The
Independent
Six
scientists from some of the leading scientific institutions in the United
States have issued what amounts to an unambiguous warning to the world:
civilisation itself is threatened by global warming.
They also implicitly criticise
the UN's Intergovernmental Panel on Climate Change (IPCC) for underestimating
the scale of sea-level rises this century as a result of melting glaciers
and polar ice sheets.
Instead of sea levels rising
by about 40 centimetres, as the IPCC predicts in one of its computer
forecasts, the true rise might be as great as several metres by 2100.
That is why, they say, planet Earth today is in "imminent peril".
In a densely referenced scientific
paper published in the Philosophical Transactions of the Royal Society
A some of the world's leading climate researchers describe in detail
why they believe that humanity can no longer afford to ignore the "gravest
threat" of climate change.
"Recent greenhouse gas
emissions place the Earth perilously close to dramatic climate change
that could run out of control, with great dangers for humans and other
creatures," the scientists say. Only intense efforts to curb man-made
emissions of carbon dioxide emissions and other greenhouse gases can
keep the climate within or near the range of the past one million years,
they add.
The researchers were led
by James Hansen, the director of Nasa's Goddard Institute for Space
Studies, who was the first scientist to warn the US Congress about global
warming.
The other scientists were
Makiko Sato, Pushker Kharecha and Gary Russell, also of the Goddard
Institute, David Lea of the University of California, Santa Barbara,
and Mark Siddall of the Lamont-Doherty Earth Observatory at Columbia
University in New York.
In their 29-page paper, "Climate
Change and trace gases", the scientists frequently stray from the
non-emotional language of science to emphasise the scale of the problems
and dangers posed by climate change.
In an email to The Independent,
Dr Hansen said: "In my opinion, among our papers this one probably
does the best job of making clear that the Earth is getting perilously
close to climate changes that could run out of our control."
The unnatural "forcing"
of the climate as a result of man-made emissions of carbon dioxide and
other greenhouse gases threatens to generate a "flip" in the
climate that could "spark a cataclysm" in the massive ice
sheets of Antarctica and Greenland, the scientists write.
Dramatic flips in the climate
have occurred in the past but none has happened since the development
of complex human societies and civilisation, which are unlikely to survive
the same sort of environmental changes if they occurred now.
"Civilisation developed,
and constructed extensive infrastructure, during a period of unusual
climate stability, the Holocene, now almost 12,000 years in duration.
That period is about to end," the scientists warn. Humanity cannot
afford to burn the Earth's remaining underground reserves of fossil
fuel. "To do so would guarantee dramatic climate change, yielding
a different planet from the one on which civilisation developed and
for which extensive physical infrastructure has been built," they
say.
Dr Hansen said we have about
10 years to put into effect the draconian measures needed to curb CO2
emissions quickly enough to avert a dangerous rise in global temperature.
Otherwise, the extra heat could trigger the rapid melting of polar ice
sheets, made far worse by the "albedo flip" - when the sunlight
reflected by white ice is suddenly absorbed as ice melts to become the
dark surface of open water.
The glaciers and ice sheets
of Greenland in the northern hemisphere, and the western Antarctic ice
sheet in the south, both show signs of the rapid changes predicted with
rising temperatures. "
The albedo flip property
of ice/water provides a trigger mechanism. If the trigger mechanism
is engaged long enough, multiple dynamical feedbacks will cause ice
sheet collapse," the scientists say. "We argue that the required
persistence for this trigger mechanism is at most a century, probably
less."
The latest assessment of
the IPCC published earlier this year predicts little or no contribution
to 21st century sea level from Greenland or Antarctica, but the six
scientists dispute this interpretation. "The IPCC analyses and
projections do not well account for the nonlinear physics of wet ice
sheet disintegration, ice streams and eroding ice shelves, nor are they
consistent with the palaeoclimate evidence we have presented for the
absence of discernible lag between ice sheet forcing and sea-level rise,"
the scientists say.
Their study looked back over
more than 400,000 years of climate records from deep ice cores and found
evidence to suggest that rapid climate change over a period of centuries,
or even decades, have in the past occurred once the world began to heat
up and ice sheets started melting. It is not possible to assess the
dangerous level of man-made greenhouse gases.
"However, it is much
lower than has commonly been assumed. If we have not already passed
the dangerous level, the energy infrastructure in place ensures that
we will pass it within several decades," the scientists say in
their findings.
"We conclude that a
feasible strategy for planetary rescue almost surely requires a means
of extracting [greenhouse gases] from the air."
© 2007 Independent News
and Media Limited
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