[A-List] Global Warming: The vicious circle

[Bill Totten <shimogamo@xxxxxxxxxxxxx>]

by Steve Connor, Science Editor

The Independent & The Independent on Sunday

Independent.co.uk Online Edition (January 29 2007)


The effects of man-made emissions of carbon dioxide are being felt on every
inhabited continent in the world with very different parts of the climate now
visibly responding to human activity.

These are among the main findings of the most intensive study of climate change
by 2,000 of the world's leading climate scientists. They conclude that there is
now little doubt that human activity is changing the face of the planet.

In addition to rising surface temperatures around the world, scientists have now
linked man-made emissions of greenhouse gases to significant increases in ocean
temperatures, rises in sea levels and the dramatic melting of Arctic sea ice
over the past 35 years.

A draft copy of the fourth report of the Intergovernmental Panel on Climate
Change (IPCC) says that global temperature rises this century of between two and
4.5 degrees Celsius are almost inevitable. Ominously, however, it also says that
much higher increases of six degrees Celsius "or more" cannot be ruled out.

The final version of the IPCC's latest report is to be published on Friday but a
draft copy, seen by The Independent, makes it clear that climate change could be
far worse than previously thought because of potentially disastrous "positive"
feedbacks which could accelerate rising temperatures.

A warmer world is increasing evaporation from the oceans causing atmospheric
concentrations of water vapour, a powerful greenhouse agent, to have increased
by four per cent over the sea since 1970. Water vapour in the atmosphere
exacerbates the greenhouse effect. This is the largest positive feedback
identified in the report, which details for the first time the IPCC's concern
over the uncertainties - and dangers - of feedback cycles that may quickly
accelerate climate change.

All the climate models used by the IPCC also found that rising global
temperatures will erode the planet's natural ability to absorb man-made carbon
dioxide. This could lead to carbon dioxide concentrations in the atmosphere
rising by a further 44 per cent, causing global average temperatures to increase
by an additional 1.2 Celsius by 2100.

The IPCC's Fourth Assessment Report will go further than any of its three
previous reports in linking the clear signs of global climate change with
increases in man-made emissions of carbon dioxide and other greenhouse gases
since the start of the Industrial Revolution.

"Confidence in the assessment of the human contributions to recent climate
change has increased considerably since the Third Assessment Report", says the
draft report. This is due to the stronger signs of climate change emerging from
longer and more detailed records and scientific observations, it says.

The "anthropogenic signal" - the visible signs of human influence on the climate
- has now emerged not just in global average surface temperatures, but in global
ocean temperatures and ocean heat content, temperature extremes on the land and
the rapidly diminishing Arctic sea ice. "Anthropogenic warming of the climate
system is widespread and can be detected in temperature observations taken at
the surface, in the free atmosphere and in the oceans", the draft report says.
"It is highly likely [greater than 95 per cent probability] that the warming
observed during the past half century cannot be explained without external
forcing [human activity]."

The report adds that global warming over the past fifty years would have been
worse had it not been for the counterbalancing influence of man-made emissions
of aerosol pollutants, tiny airborne particles that reflect sunlight to cause
atmospheric cooling. "Without the cooling effect of atmospheric aerosols, 
it is likely that greenhouse gases alone would have caused more global mean
temperature rise than that observed during the last fifty years", the draft
report says.

"The hypothetical removal from the atmosphere of the entire current burden of
anthropogenic sulphate aerosol particles would produce a rapid increase of about
0.8 degrees Celsius within a decade or two in the globally averaged temperature."

The IPCC says that over the coming century we are likely to see big changes to
the Earth's climate system. These include:

* Heat waves, such as the one that affected southern Europe in summer 2003, 
are expected to be more intense, longer-lasting and more frequent.

* Tropical storms and hurricanes are likely to be stronger, 
with increased rainfall and higher storm surges flooding coastlines.

* The Arctic is likely to become ice free in the summer, and there will be
continued melting of mountain glaciers, ice caps and ice sheets.

* Sea levels will rise significantly even if levels of carbon dioxide are
stabilised. By 2100 sea levels could be 0.43 metres higher on average than
present, and by 2300 they could be up to 0.8 metres higher.

The IPCC also finally nails the canard of the climate sceptics who argue that
global warming is a myth or the result of natural climate variability; natural
factors alone cannot account for the observed warming, the IPCC says. "These
changes took place at a time when non-anthropogenic forcing factors (that is,
the sum of solar and volcanic forcing) would be expected to have produced
cooling, not warming.

"There is increased confidence that natural internal variability cannot account
for the observed changes, due in part to improved studies demonstrating that the
warming occurred in both oceans and atmosphere, together with observed ice mass
losses".

The report, the first draft of which was formulated last year, 
will be made public on Friday in Paris.


Key findings of the IPCC's fourth assessment report

* Global temperatures continue to rise with eleven of the twelve warmest years
since 1850 occurring since 1995. Computer models suggest a further rise of about
three degrees Celsius by 2100, with a six degrees Celsius rise a distant
possibility

* It is virtually certain (there is more than a 99 per cent probability) that
carbon dioxide levels and global warming is far above the range of natural
variability over the past 650,000 years

* It is virtually certain that human activity has played the dominant role 
in causing the increase of greenhouse gases over the past 250 years

* Man-made emissions of atmospheric aerosol pollutants have tended to counteract
global warming, which otherwise would have been significantly worse

* The net effect of human activities over the past 250 years has very likely
exerted a warming influence on the climate

* It is likely that human activity is also responsible for other observed
changes to the Earth's climate system, such as ocean warming and the melting 
of the Arctic sea ice

* Sea levels will continue to rise in the 21st Century because of the thermal
expansion of the oceans and loss of land ice

* The projected warming of the climate due to increases in carbon dioxide during
the 21st Century is likely to cause the total melting of the Greenland ice sheet
during the next 1,000 years, according to some computer forecasting models

* The warm Gulf Stream of the North Atlantic is likely to slow down during the
21st Century because of global warming and the melting of the freshwater locked
up in the Greenland ice sheet. But no models predict the collapse of that warm
current by 2100.

Also in this section

    * Where have all the birds gone?
    * Shark! The great white fight and the creature from the deep
    * Ice island the size of London threatens rigs
    * Chic & cheerful (but not so great for the environment)
    * Girl, 12, is fined for failing to recycle cardboard box

(c) 2006 Independent News and Media Limited

http://news.independent.co.uk/environment/article2193672.ece

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