'Sun not behind global warming'

• Leigh Dayton, Science writer
• July 10, 2007

THE key plank of a controversial British documentary has been discredited by new research showing that the sun is not causing global warming.

The findings are in stark contrast to claims made in the documentary The Great Global Warming Swindle, which is to be shown on ABC television on Thursday.

The program dismisses the widely held conclusion that greenhouse gases from human activity are driving global warming, instead claiming that changes in solar activity have triggered recent warming.

"Manmade global warming is unmitigated nonsense," the program's writer and director, Martin Durkin, wrote in last Saturday's The Weekend Australian.

But solar physicists at Britain's Rutherford Appleton Laboratory and the University of Southampton, along with colleague Claus Froehlich of the World Radiation Centre in Dorf, Switzerland, have found that while solar activity may have played a role in climate change in the first half of the last century, it is not driving the recent rapid warming.

Their conclusion was based on a study of all the available solar data for the past 100 years.

They found no correlation between total solar radiation, the number of sun spots or cosmic ray intensity and global warming since 1985.

"Our results show that the observed rapid rise in global mean temperatures seen after 1985 cannot be ascribed to solar variability," they will report this week in the Proceedings of the Royal Society A.

University of Melbourne climate scientist David Karoly commented: "These findings completely refute the allegations made by some pseudo-scientists that all recent global warming is due to solar effects."

Professor Karoly has just returned to Australia as a Federation Fellow from the University of Oklahoma, where he took part as a lead author in the Intergovernmental Panel on Climate Change assessment released last April.

As reported by The Australian at the time, Professor Karoly was highly critical of efforts by panel delegates from China, Saudi Arabia and Russia to water down the scientific findings.

Professor Karoly will appear on an expert panel after the documentary is broadcast, along with climate change sceptic Bob Carter of James Cook University.

Mike Lockwood, a professor at the Rutherford laboratory, told the journal Nature that he and Dr Froehlich were "galvanised" to conduct a new and comprehensive study of solar data following allegedly misleading media reports about global warming, including those made in Mr Durkin's documentary, which screened in Britain in March.

Despite their findings, Israeli scientist Nir Shaviv, of the Hebrew University of Jerusalem, continued to support the solar theory. He told Nature the new findings may not reflect a "lag" between solar activity and warming.

Along with Urs Neu, of the climate and global change forum of the Swiss Academy of Sciences in Berne, Professor Karoly dismissed Dr Shaviv's suggestion.

"We have much evidence (from different types of research) that most of the observed warming over the last 20 to 30 years is not due to solar influences," Professor Karoly said.