A surreal scientific blunder last week raised a huge question mark about the temperature records that underpin the worldwide alarm over global warming. On Monday, Nasa's Goddard Institute for Space Studies (GISS), which is run by Al Gore's chief scientific ally, Dr James Hansen, and is one of four bodies responsible for monitoring global temperatures, announced that last month was the hottest October on record.
This was startling. Across the world there were reports of unseasonal snow and plummeting temperatures last month, from the American Great Plains to China, and from the Alps to New Zealand. China's official news agency reported that Tibet had suffered its "worst snowstorm ever". In the US, the National Oceanic and Atmospheric Administration registered 63 local snowfall records and 115 lowest-ever temperatures for the month, and ranked it as only the 70th-warmest October in 114 years.
So what explained the anomaly? GISS's computerised temperature maps seemed to show readings across a large part of Russia had been up to 10 degrees higher than normal. But when expert readers of the two leading warming-sceptic blogs, Watts Up With That and Climate Audit, began detailed analysis of the GISS data they made an astonishing discovery. The reason for the freak figures was that scores of temperature records from Russia and elsewhere were not based on October readings at all. Figures from the previous month had simply been carried over and repeated two months running.
The error was so glaring that when it was reported on the two blogs - run by the US meteorologist Anthony Watts and Steve McIntyre, the Canadian computer analyst who won fame for his expert debunking of the notorious "hockey stick" graph - GISS began hastily revising its figures. This only made the confusion worse because, to compensate for the lowered temperatures in Russia, GISS claimed to have discovered a new "hotspot" in the Arctic - in a month when satellite images were showing Arctic sea-ice recovering so fast from its summer melt that three weeks ago it was 30 per cent more extensive than at the same time last year.
A GISS spokesman lamely explained that the reason for the error in the Russian figures was that they were obtained from another body, and that GISS did not have resources to exercise proper quality control over the data it was supplied with. This is an astonishing admission: the figures published by Dr Hansen's institute are not only one of the four data sets that the UN's Intergovernmental Panel on Climate Change (IPCC) relies on to promote its case for global warming, but they are the most widely quoted, since they consistently show higher temperatures than the others.
If there is one scientist more responsible than any other for the alarm over global warming it is Dr Hansen, who set the whole scare in train back in 1988 with his testimony to a US Senate committee chaired by Al Gore. Again and again, Dr Hansen has been to the fore in making extreme claims over the dangers of climate change. (He was recently in the news here for supporting the Greenpeace activists acquitted of criminally damaging a coal-fired power station in Kent, on the grounds that the harm done to the planet by a new power station would far outweigh any damage they had done themselves.)
Yet last week's latest episode is far from the first time Dr Hansen's methodology has been called in question. In 2007 he was forced by Mr Watts and Mr McIntyre to revise his published figures for US surface temperatures, to show that the hottest decade of the 20th century was not the 1990s, as he had claimed, but the 1930s.
Another of his close allies is Dr Rajendra Pachauri, chairman of the IPCC, who recently startled a university audience in Australia by claiming that global temperatures have recently been rising "very much faster" than ever, in front of a graph showing them rising sharply in the past decade. In fact, as many of his audience were aware, they have not been rising in recent years and since 2007 have dropped.
Dr Pachauri, a former railway engineer with no qualifications in climate science, may believe what Dr Hansen tells him. But whether, on the basis of such evidence, it is wise for the world's governments to embark on some of the most costly economic measures ever proposed, to remedy a problem which may actually not exist, is a question which should give us all pause for thought.
