[Texgreen] The Earth today stands in imminent peril

[Roger Baker]

...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....

                         
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<http://environment.independent.co.uk/climate_change/article2675747.ece>

     The Earth today stands in imminent peril

...and nothing short of a planetary rescue will save it from the  
environmental cataclysm of dangerous climate change. Those are not  
the words of eco-warriors but the considered opinion of a group of  
eminent scientists writing in a peer-reviewed scientific journal.

By Steve Connor, Science Editor
Published: 19 June 2007

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."