Published: Friday, 18 May, 2007, 01:17 PM Doha Time
By Michael McCarthy
LONDON:
The Earth’s ability to soak up the greenhouse gases causing global warming is starting to fail because of rising temperatures, in a long-feared sign of “positive feedback,” new research reveals.
Climate change itself is weakening one of the principal “sinks” absorbing carbon dioxide from the atmosphere – the Southern Ocean around Antarctica – a new study has found.
As a result, atmospheric CO2 levels in the coming decades may rise faster, and bring about rising temperatures more quickly, than previously anticipated. Stabilising 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 - at the moment a distant prospect.
But 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, universally regarded as inadequate.
“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.
“That makes it all the more important that they reach an agreement to kick-start the important talks on the second phase of Kyoto.” The shift that has been detected in a four-year study by researchers from the University of East Anglia (UEA), the British Antarctic Survey (BAS) 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 defences against global warming.
Human society has hugely benefited from the Earth’s natural carbon absorption facility, which means that the oceans and forests between them take up roughly half of the vast amount of CO2 pumped out from industry and transport every year, 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 (thus intensifying climate change). Although supercomputer models of the climate have for some time predicted the weakening of both the ocean and terrestrial sinks with global warming, no example of it happening has actually been detected - until now.
Now the research team has found that the vast Southern Ocean, which is the biggest of the Earth’s carbon sinks, accounting for about 15% of the planet’s 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 by human activities has grown by 40%, so the sink has stopped keeping pace with the increase, and much more CO2 is remaining behind in the atmosphere to trap the sun’s heat.
The effect, which was revealed by scrutinising 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 deep in the water closer to the surface - which reduces the ability of the surface to absorb the gas from the air.
The increased wind speeds are themselves believed to be caused by altered atmospheric temperature regimes produced by two separate processes - the depletion of the Earth’s ozone layer over Antarctica by chlorofluorocarbon gases from aerosol spray cans (which have now been 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 be harder to control, than is generally appreciated. The pessimism about the future of scientists such as James Lovelock is largely based on the fact that most of the 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 Quere 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 tonnes] of carbon emitted into the atmosphere by humans. The possibility that in a warmer world the Southern Ocean - the strongest ocean sink - is weakening, is a cause for concern.”
He added: “It’s another significant warning that we’ve got to be very careful about what we’re doing. It is a piece of evidence that says the system is responding [to climate change] in a way that’s not helping us. The ocean has been helping us, but this is a sign that we cannot rely on it to do so.”
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 it was affecting the whole of the ocean, or merely the Southern Ocean as a localised phenomenon, he said.
In recent years it has become clear that the rate at which CO2 was accumulating in the atmosphere is itself increasing. The level currently stands at about 382 parts per million by volume (ppm), up from 315ppm when regular measurements started in 1958.
In the last decade the rate of increase has jumped from about 1.6ppm annually to well above 2ppm per year - a fact which, as the Independent reported in October 2004, may well signal not just that more CO2 is being pumped out by industry and transport, but that the earth’s absorption ability itself is shrinking.
Asked if this rate increase could now be linked to weakening sinks, Dr Le Quere said: “I think we are just at the border of detecting that.” She added: “All the carbon cycle experts have their eyes on it. They’re all trying to detect whether we can see changes in the airborne fraction and whether we can attribute them to changes in carbon sinks, but we can’t say it yet.”
l “Saturations of the Southern Ocean CO2 sink due to recent climate change.” Le Quere et al, published this week in Science. – The Independent

WARMING TO CHANGE
Feedback: it’s a phenomenon you’ll be hearing a lot more of. In its initial incarnation, feedback was harmless. It first sprang to prominence (you may remember if you’re an old rocker) as the name for a musical effect employed by The Who and other loud rock bands to jack up the noise level.
But this feature of cybernetics (the control of systems) is a lot more serious when it comes to the possible progress of global warming. It is what happens when a part of the output of a process or a system returns to affect the input.
Negative feedback, which occurs when what comes out lessens the strength of what subsequently goes in, tends to suppress the original process (this happens with the valve regulating a steam engine).
Positive feedback, on the other hand, which occurs when the output goes back to add force to the input, can magnify the whole process until it takes on a “runaway” character.
The fear of some climate scientists is that just such a positive feedback might occur with global warming, in which the warming itself precipitates changes in the earth’s natural systems, which themselves cause additional warming, which then causes further changes, and so on, in an unstoppable acceleration.
This fear is well founded, because records of ancient climates deduced from cores driven deep into the polar ice show that this has happened in the past: previous episodes of warming at the end of ice ages have indeed developed a runaway character, with enormous temperature rises of as much as 10C in 50 years.
There are a string of potential feedbacks associated with climate change, nearly all of them likely to intensify the process. One, for example, concerns the melting of the ice cover of the Arctic ocean, which climate models suggest will be gone by 2080 - or even considerably earlier.
This will not just be fatal for polar bears (which need the ice to hunt seals). It will replace a huge, bright white surface which reflects back much of the sun’s radiation (the ice) with a dark one (the sea) which will absorb it - thus contributing to a warming planet.
But it is the failure of the ocean and forest carbon sinks in a warming world which is the most serious potential feedback of all, because of the vast amounts of greenhouse gases they take up. It is predicted by the supercomputer climate models that this will eventually happen, in the decades to come - but what this week’s new research alarmingly indicates is that the process is happening already. – The Independent

http://www.gulf-times.com/site/topics/article.asp?cu_no=2&item_no=149887&version=1&template_id=46&parent_id=26