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.

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.

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.

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.