Earth’s
Natural Defenses Against Climate Change ‘Beginning To Fail’
By Michael McCarthy
19 May, 2007
The
Independent
The
earth’s ability to soak up the gases causing global warming is
beginning to fail because of rising temperatures, in a long-feared sign
of “positive feedback,” new research reveals today.
Climate change itself is
weakening one of the principal “sinks” absorbing carbon
dioxide - the Southern Ocean around Antarctica - a new study has found.
As a result, atmospheric
CO2 levels may rise faster and bring about rising temperatures more
quickly than previously anticipated. Stabilizing the CO2 level, which
must be done to bring the warming under control, is likely to become
much more difficult, even if the world community agrees to do it.
The news may give added urgency
to the meeting in three weeks’ time between the G8 group of rich
nations and the leading developing countries led by China, at Heiligendamm
in Germany, when an attempt will be made to put together the framework
of a new world climate treaty to succeed the current Kyoto protocol.
“This is a timely warning
in advance of Heiligendamm and the G8 that the climate clock is beginning
to tick faster,” said the leading environmentalist Tom Burke,
visiting professor at Imperial College London.
“The shift that has
been detected in a four-year study by researchers from the University
of East Anglia, the British Antarctic Survey and the Max-Planck Institute
for Biogeochemistry, published in the journal Science, is one of the
most ominous in the development of climate change. It implies a breach
in the planet’s own defenses against global warming.
Human society has hugely
benefited from the earth’s natural carbon absorption facility,
which means oceans and forests take up roughly half of the CO2 pumped
into the atmosphere, in the so-called carbon cycle. What is left in
the atmosphere is known as the “airborne fraction”.
If sinks weakened, the airborne
fraction would be likely to get bigger. Although supercomputer models
of the climate have for some time predicted the weakening of the ocean
and terrestrial sinks, no example of it happening has actually been
detected - until now.
Now the research team has
found the vast Southern Ocean, which is the earth’s biggest carbon
sink, accounting for about 15 per cent of the total absorption potential,
has become effectively CO2-saturated.
The level of the gas it is
absorbing has remained static since 1981 - but in that time the amount
emitted has grown by 40 per cent, so it has stopped keeping pace and
much more CO2 is left over to trap the sun’s heat.
The effect - revealed by
scrutinizing observations of atmospheric CO2 from 40 stations around
the world, is thought to have been caused by an increase in ocean wind
speeds. Stormier weather and stronger waves are churning up the sea
and bringing natural CO2 stored there closer to the surface - which
reduces the ability of the surface to absorb the gas from the air.
The increased winds are believed
to be caused by altered atmospheric temperature regimes produced by
two separate processes - the depletion of the ozone layer over Antarctica
by chlorofluorocarbon gases from aerosol spray cans (now phased out),
and global warming.
It is thus a positive feedback
- an effect of climate change which itself makes climate change worse.
Some researchers fear that feedbacks may make global warming happen
much faster, and harder to control, than generally appreciated. The
pessimism of scientists such as James Lovelock is largely based on the
fact that most feedbacks in the earth’s system are likely to work
against us.
“This is the first
unequivocal detection of a carbon sink weakening because of recent climate
change,” said the lead author of the study, Corinne Le Quéré,
of the University of East Anglia. “This is serious. Whenever the
world has greatly warmed in the past, the weakening of CO2 sinks has
contributed to it.”
Professor Chris Rapley, director
of the British Antarctic Survey, said: “Since the beginning of
the Industrial Revolution the world’s oceans have absorbed about
a quarter of the 500 gigatons [millions of tons] of carbon emitted by
humans. The possibility that in a warmer world the Southern Ocean is
weakening is a cause for concern.”
The Government’s chief
scientific adviser, Sir David King, said: “We have quite a large
number of positive feedbacks to worry about, and this appears to be
another one. But the seriousness of it would depend on if it was affecting
the whole ocean, or merely the Southern Ocean.”
In recent years it has become
clear that the rate at which CO2 was accumulating is itself increasing.
The level currently stands at about 382 parts per million by volume
(ppm), up from 315 ppm in 1958.
In the past decade the rate
has jumped from about 1.6ppm annually to well above 2ppm - a fact which,
as The Independent reported in October 2004, may well signal that the
earth’s absorption ability is shrinking.
Asked if this rate increase
could now be linked to weakening sinks, Dr Le Quéré said:
“I think we are just at the border of detecting that.” She
added: “All the carbon cycle experts have their eyes on it.”
Saturations of the Southern
Ocean CO2 sink due to recent climate change, Le Quéré
et al, published this week in Science
© 2007 Independent News
and Media Limited
Digg
it! And spread the word!
Here is a unique chance to help this article to be read by thousands
of people more. You just Digg it, and it will appear in the home page
of Digg.com and thousands more will read it. Digg is nothing but an
vote, the article with most votes will go to the top of the page. So,
as you read just give a digg and help thousands more to read this article.
Click
here to comment
on this article