Peter Laut, a former adviser to the Danish Energy Agency who first identified the flaws, said there were practically no observations to support the idea that variations in sunspots played more than a minor role in global warming.

Mr Laut's analysis of the flaws is accepted by ... Paul Crutzen, an atmospheric chemist at the Max Planck Institute in Germany, who won a Nobel Prize for his work on understanding the hole in the ozone layer. "There is definitely a problem [with these studies]. Laut has really pinned it down but the [sunspot] argument keeps reappearing and its quite irritating," Professor Crutzen said.

Professor Stefan Rahsmstorf, of Potsdam University, agreed: "I've looked into this quite closely and I'm on Laut's side in terms of his analysis of the data."


"Their controversial papers must be retracted or at least that there will be an official statement by them acknowledging their mistake," said Andre Berger, honorary president of the European Geosciences Union.