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Research shows no link between solar activity, global warming
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07:50, July 12, 2007

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A new research confirmed that solar activity has no link with recent global warming, New Scientist reported Wednesday on its website.

Direct satellite measurements of solar activity show it has been declining since the mid-1980s and cannot account for recent rises in global temperatures, said leading researcher Mike Lockwood of the Rutherford Appleton Laboratory, part of the Science and Technology Facilities Council in the UK.

Looking at data from the past 40 years, Lockwood and his colleague at the World Radiation Center in Switzerland noticed that solar activity did a "U-turn in every possible way" in the mid-1980s.

"The upshot is that somewhere between 1985 and 1987 all the solar factors that could have affected climate have been going in the wrong direction. If they were really a big factor we would have cooling by now," Lockwood was quoted as saying.

According to the researchers, the number of sunspots peaked twice during the 20th century, once in 1960 and then again in 1985, but have been dropping since.

Sunspots are used as indicators of solar activity, and people have tried to link the growing number of sunspots during the 20th century with rising global temperatures.

The two researchers' results show that cosmic rays, which help generate clouds and cool the atmosphere, reached a minimum around 1985 and have risen since, and correspondingly, the magnetic field that shields Earth from cosmic rays also reached a maximum at about the same time, in 1987.

The data suggests solar activity is playing a negligible role in current global warming: irradiance rose between 1977 and 1985, but has been dropping since, the researchers said.

The only way of reconciling the data with the idea that solar activity is causing global warming is to propose that there is a time lag between the Sun's activity changing and those changes affecting the Earth's climate, Lockwood said, adding that but even with a lag, climatologists would have noticed a slow-down in the rate at which temperatures are rising around the globe.

They have had 20 years of the cosmic rays and the irradiance going in the wrong direction, and yet they've not yet seen any effect on temperatures, Lockwood said, adding it would have to be an extremely long lag -- at least 50 years -- which would invalidate a lot of the previous sun-climate proposals.

The researchers' results suggest that even the Intergovernmental Panel on Climate Change (IPCC) has overestimated the Sun's influence on the Earth's climate. The IPCC published in February a report stating that the Sun had roughly 10 percent of the warming effect of human activities.

Source: Xinhua

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