In a highly controversial paper, climate scientists at three US universities have contested claims that greenhouse gases were causing climate change and instead attributed it to earth's 'natural cycle'.

Scientists at the University of Rochester, the University of Alabama, and the University of Virginia have said that the observed patterns of temperature changes over the last 30 years are not in accord with what greenhouse models predict.

These observations are in conflict with the conclusions of the United Nations Intergovernmental Panel on Climate Change and also with some recent research publications based on essentially the same data.

However, they are supported by the results of the US-sponsored Climate Change Science Program.

Dr Fred Singer, president of the Science and Environmental Policy Project and co-author of Unstoppable Global Warming, says that the current warming trend is simply part of a natural cycle of climate warming and cooling that has been seen in ice cores, deep-sea sediments and stalagmites and published in hundreds of papers in peer-reviewed journals.

The mechanism for producing such cyclical climate change is still under discussion; but they are most likely caused by variations in the 'solar wind' that affect the flux of cosmic rays incident on the earth's atmosphere and influence cloudiness  and thus the climate, he adds.

"Our research demonstrates that the ongoing rise of atmospheric carbon dioxide makes only a minor contribution to climate warming. We must conclude, therefore, that attempts to control carbon dioxide emissions are ineffective and pointless while very costly," Singer adds.

Once one accepts the evidence that carbon dioxide is insignificant in warming the climate, all kinds of consequences follow logically and have a profound effect on energy policy, he says.