'Runaway climate change' 'unrealistic', say scientists

Amazon rainforest

As climate scientists are cleared of wrongdoing on two fronts, yet another much-cherished theory is challenged

BY Tim Edwards LAST UPDATED AT 16:17 ON Wed 7 Jul 2010

As the scientific community seeks to put a lid on the outpouring of climate change scepticism unleashed in the wake of Climategate and the publicising of flaws in a UN climate report, a new study has suggested that the theory of 'runaway climate change' is "unrealistic".

Today, Sir Muir Russell's independent review of the Climategate scandal, in which hackers stole and circulated emails from the Climatic Research Unit at the University of East Anglia, cleared climate scientists of malpractice. It is the third inquiry to do so – leading to calls of 'whitewash' from climate change sceptics.

And in another boost for climate science, a Dutch government review yesterday gave the all-clear to a United Nations report which had been widely criticised for overstating the threat of climate change and containing bogus claims about the probable effects.

The Netherlands Environmental Assessment Agency (PBL) said the Intergovernmental Panel on Climate Change's 2007 report contained "no errors that would undermine the main conclusions" that climate change will have serious effects for the world. The 35 errors it did find were mainly typographical or similarly trivial. The IPCC has accepted 12 of them.

Embarrassingly for PBL, it had to admit it was the source of one of the most glaring errors – a claim that 55 per cent of the Netherlands was at risk of flooding because it lies under sea level.

Despite two days of good news for climate scientists, a new study is set to rock the boat again by calling into question one of the more frightening global warming scenarios: 'runaway climate change'. Under this scenario, rising temperatures speed up processes that catastrophically increase the rate of global warming – a positive feedback loop.

One of these processes is an increase in the rate of carbon dioxide (CO2) production by plants and microorganisms in the soil caused by an increase in temperature. As CO2 is a greenhouse gas, it has been suggested this will further increase temperatures, leading to a further increase in CO2 production until the Earth is too hot for human life.

Using Fluxnet, a global network of more than 250 'flux towers' to sample CO2 concentrations, a team of researchers from the Max Planck Institute has found that, actually, temperature has a much smaller effect on CO2 release than previous studies claimed.

The researchers, led by Miguel Mahecha, found that the rate at which plants and microorganisms produce CO2 in ecosystems from tropical rainforests to savannah does not even double when the temperature increases by 10°C from one week to the next.

His colleague Markus Reichstein says: "Particularly alarmist scenarios for the feedback between global warming and ecosystem respiration (CO2 production) thus prove to be unrealistic."

Climate change sceptics might say the new study is yet another nail in the coffin of the IPCC report, which says: "Anthropogenic warming could lead to some effects that are abrupt or irreversible, depending upon the rate and magnitude of the climate change."

But mainstream scientists will just be pleased that Fluxnet has given them real-world measurements upon which to base their computer models - which could be another nail in the coffin of climate change scepticism, relying as it so often does on quibbles over the quality of data. · 

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