Financial Times (London, U.K.), May 15, 2008

CLIMATE CHANGE STUDY POINTS FINGER

[Rachel's introduction: Scientists have been able to say with virtual certainty for the first time that the climate change observed over the past four decades is not the result of natural phenomena but is caused by human activities.]

By Fiona Harvey

Scientists have been able to say with virtual certainty for the first time that the climate change observed over the past four decades is not the result of natural phenomena but is man made.

The research compounds the conclusion of the biggest scientific report on global warming to date, the fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC) last year, which asserted a strong likelihood that human action was changing the climate.

The new study raises the likelihood of "unnatural" causes of global warming to near certainty.

Authors of the study, published today 6 Mbyte PDF in the peer reviewed journal Nature, examined a greater range of data than any other study so far. "Changes in natural systems since at least 1970 are occurring in regions of observed temperature increases, and these temperature increases at continental scales cannot be explained by natural climate variations alone," they say.

They give warning that man-made climate change is having "a significant impact on physical and biological systems globally". The authors of the Nature study, including scientists from the Australia, China, the US and several other countries, found that more than 90 per cent of the data sets they examined showed evidence that natural systems were responding to warming.

Spring is coming earlier, permafrost is melting and coastal erosion is increasing under the influence of rising sea levels, while animals and birds are changing their migration and reproductive patterns.

Barry Brook, director of climate change research at the University of Adelaide, said: "[We should] consider that there has been only 0.75ºC of temperature change so far, yet the expectation for this century is four to nine times that amount.

"So these changes are only a minor portent of what is likely to come, especially if we continue on our carbon-profligate pathway."

Climate scientists know they may be facing difficult times ahead in persuading the public and politicians of the urgency of global warming, as research published recently in Nature suggested that global temperatures were not likely to increase in the next decade, and could even decline.

Scientists from Germany's Leibniz Institute of Marine Sciences and the UK Met Office's Hadley Centre say natural variations in the climate linked to the Pacific cooling system known as La Nina, and a cooling phase of a system of Atlantic currents called the meridional overturning circulation, may push down temperatures despite the effects of greenhouse gases.

After those effects wear off, within about a decade, temperatures are likely to rise much more strongly as the warming effect of carbon emissions regains the upper hand in altering the climate.

Scientists fear that the expected lull in temperature rises might dispel any sense of urgency in tackling global warming and provide ammunition for climate change sceptics.

Copyright 2008 The Financial Times Limited