95 per cent chance that Man is to blame for global warming, say scientists

Ben Webster, Environment Editor
Times Online

The evidence that human activity is causing global warming is much stronger than previously stated and is found in all parts of the world, according to a study that attempts to refute claims from sceptics.

The “fingerprints” of human influence on the climate can be detected not only in rising temperatures but also in the saltiness of the oceans, rising humidity, changes in rainfall and the shrinking of Arctic Sea ice at the rate of 600,000 sq km a decade.

The study, by senior scientists from the Met Office Hadley Centre, Edinburgh University, Melbourne University and Victoria University in Canada, concluded that there was an “increasingly remote possibility” that the sceptics were right that human activities were having no discernible impact. There was a less than 5 per cent likelihood that natural variations in climate were responsible for the changes.

The study said that the Intergovernmental Panel on Climate Change (IPCC) had understated mankind’s overall contribution to climate change. The IPCC had said in 2007 that there was no evidence of warming in the Antarctic. However, the panel said that the latest observations showed that man-made emissions were having an impact on even the remotest continent.

The panel assessed more than 100 recent peer-reviewed scientific papers and found that the overwhelming majority had detected clear evidence of human influence on the climate.

Peter Stott, head of climate monitoring and attribution at the Met Office, who led the study, said: “This wealth of evidence we have now shows there is an increasingly remote possibility of climate change being dominated by natural factors rather than human factors.”

However, a section of the study that said changes in hurricane activity were poorly understood is likely to be seized on by sceptics, who argue that disasters such as Hurricane Katrina have been falsely blamed on man-made global warming. Publication of the research in the journal Wiley Interdisciplinary Reviews: Climate Change comes as two inquiries are being held into accusations, based on leaked e-mails, that scientists at the University of East Anglia manipulated and suppressed climate data.

The study found that since 1980, the average global temperature had increased by about 0.5C and that the Earth was continuing to warm at the rate of about 0.16C a decade. This trend is reflected in measurements from the oceans. Warmer temperatures had led to more evaporation from the surface, most noticeably in the sub-tropical Atlantic, said Dr Stott. As a result, the sea was getting saltier. Evaporation in turn affected humidity and rainfall. The atmosphere was getting more humid, as climate models had predicted, and amplifying the water cycle. This meant that more rain was falling in high and low latitudes and less in tropical and sub-tropical regions.