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Updated: October 10, 2010 19:48 IST

Increase in solar activity cools the earth: Study

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An x-ray photo of the sun provided by NASA. File photo
An x-ray photo of the sun provided by NASA. File photo

In what may renew the debate over the science behind climate change, a new research has claimed that an increase in solar activity actually cools the earth.

It has been believed that sun’s activity waxes and wanes over an 11-year cycle and that when its activity wanes, the overall amount of radiation reaching the earth decreases.

Now, the new study by researchers from Imperial College London and the University of Colorado found that as solar activity decreased, the amount of light and heat reaching the earth rose rather than fell, causing the planet to become warmer.

The researchers, who looked at the sun’s activity over the period 2004-2007 when it was in a declining phase of a cycle, said a decline in the sun’s activity does not always mean that the earth becomes cooler. Its impact on melting polar ice caps, and drying up rivers could therefore have been exaggerated by conventional climate models during the period, the Telegraph reported.

The scientists also believe it may also be possible that during the next upturn of the cycle, when solar activity increases, there might be a cooling effect at the earth’s surface.

While this may support climate change sceptics’ arguments in the short term, long term analysis suggests it actually provides further evidence that the heating of the planet is more than a natural, cyclical phenomenon, they said.

Professor Joanna Haigh, from Imperial College London, who led the study, said: “These results are challenging what we thought we knew about the sun’s effect on our climate.

“However, they only show us a snapshot of the sun’s activity and its behaviour over the three years of our study could be an anomaly.

“We cannot jump to any conclusions based on what we have found during this comparatively short period and we need to carry out further studies to explore the sun’s activity and the patterns that we have uncovered on longer timescales.

“However, if further studies find the same pattern over a longer period of time, this could suggest that we may have overestimated the sun’s role in warming the planet, rather than underestimating it.”

The research, published in the journal Nature, is based on data from a satellite called SORCE (Solar Radiation and Climate Experiment) that has been measuring the sun’s energy output at X-ray, ultraviolet, visible, and near-infrared wavelengths.



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