Solar radiation is not the cause of recent global warming, two scientists say in a report published by Britain's Royal Society, the country's science organization.

The study was undertaken partly to rebut a TV documentary that argued natural solar radiation, not human activity, is the cause of global warming, the BBC reported.

The Great Global Warming Swindle was shown on Britain's Channel 4 in March. "We've almost begun to take it for granted that climate change is a manmade phenomenon," the network's website said. "But just as the environmental lobby think they've got our attention, a group of naysayers have emerged to slay the whole premise of global warming."

Mike Lockwood from the Rutherford Appleton Laboratory in Britain and Claus Fröhlich from the World Radiation Center in Switzerland dispute that. The abstract of their report in the Proceedings of the Royal Society A said there is evidence that the sun affected Earth's climate up to about 1950.

But in the past 20 years, "all the trends in the sun that could have had an influence on the Earth's climate have been in the opposite direction to that required to explain the observed rise in global mean temperatures."

Their data show that while the sun's output has fallen, temperatures on Earth have risen.

The power of the sun peaked in 1985, they reported after assessing nearly 40 years of data. Yet the Earth's average temperature has gone up 0.4 C steadily over that period, both before and after the peak.

They also studied two other measures of solar activity, solar flux and cosmic rays, and both suggested solar activity has been declining since the late 1980s.

The Royal Society endorsed the study, British media reported.

The society said: "There is a small minority which is seeking to confuse the public on the causes of climate change. They are often misrepresenting the science, when the reality is that the evidence is getting stronger every day."