The "climategate" controversy intensified last night when the senior British scientist at its centre, Professor Phil Jones, faced fresh accusations that he attempted to withhold data that could cast doubt on evidence for rising world temperatures.
The charges follow an analysis of the emails hacked from the University of East Anglia's Climatic Research Unit, of which Professor Jones is the director.
The emails, published online on the eve of the recent Copenhagen climate summit, led to allegations that Professor Jones and other researchers had behaved inappropriately in withholding or deleting scientific information to prevent its disclosure under the Freedom of Information Act (FOI). Last week the charge became more serious when the Information Commissioner's Office said that in withholding information, UEA had broken the law.
The university has set up an independent inquiry into the affair headed by Sir Muir Russell, a former vice-chancellor of the University of Glasgow, and Professor Jones has taken leave from his director's post until the inquiry is completed. But the new allegations go beyond refusing FOI requests and concern data that Professor Jones and other scientists have used to support a record of recent world temperatures that shows an upward trend.
Climate sceptics have suggested that some of the higher readings may be due not to a warmer atmosphere, but to the so-called "urban heat island effect", where cities become reservoirs of heat and are warmer than the surrounding countryside, especially during the night hours.
Professor Jones and a colleague, Professor Wei-Chyung Wang of the State University of New York at Albany suggested in an influential 1990 paper in the journal Nature that the urban heat island effect was minimal – and cited as supporting evidence a long series of temperature measurements from Chinese weather stations, half in the countryside and half in cities, supplied by Professor Wei-Chyung. The Nature paper was used as evidence in the most recent report of the UN's Intergovernmental Panel on Climate Change.
However, it has been reported that when climate sceptics asked for the precise locations of the 84 stations, Professor Jones at first declined to release the details. And when eventually he did release them, it was found that for the ones supposed to be in the countryside, there was no location given.
Climate sceptics have demanded the two professors now withdraw their heat island paper. Professor Wei-Chyung was investigated by his university, but exonerated, but the emails indicate there was also concern among Professor Jones' s colleagues at UEA, including from Dr Tom Wigley, his predecessor as head of the CRU, about the Chinese weather station data and Professor Jones's contuing reliance on it.
No-one was available for comment at the University of East Anglia last night.