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'No Sun link' to climate change Richard Black / BBC News | April 3, 2008 Scientists have produced further compelling evidence showing that modern-day climate change is not caused by changes in the Sun's activity. The research contradicts a favoured theory of climate "sceptics", that changes in cosmic rays coming to Earth determine cloudiness and temperature. The idea is that variations in solar activity affect cosmic ray intensity. Presenting their findings in the Institute of Physics journal, Environmental Research Letters, the University of Lancaster team explain that they used three different ways to search for a correlation, and found virtually none. This is the latest piece of evidence which at the very least puts the cosmic ray theory, developed by Danish scientist Henrik Svensmark at the Danish National Space Center (DNSC), under very heavy pressure. Dr Svensmark's idea formed a centrepiece of the controversial documentary The Great Global Warming Swindle. Wrong path "We started on this game because of Svensmark's work," said Terry Sloan from Lancaster University. "If he is right, then we are going down the wrong path of taking all these expensive measures to cut carbon emissions; if he is right, we could carry on with carbon emissions as normal." (Article continues below)
Cosmic rays are deflected away from Earth by our planet's magnetic field, and by the solar wind - streams of electrically charged particles coming from the Sun. The Svensmark hypothesis is that when the solar wind is weak, more cosmic rays penetrate to Earth. That creates more charged particles in the atmosphere, which in turn induces more clouds to form, cooling the climate. The planet warms up when the Sun's output is strong. Professor Sloan's team investigated the link by looking for periods in time and for places on the Earth which had documented weak or strong cosmic ray arrivals, and seeing if that affected the cloudiness observed in those locations or at those times. "For example; sometimes the Sun 'burps' - it throws out a huge burst of charged particles," he explained to BBC News. "So we looked to see whether cloud cover increased after one of these bursts of rays from the Sun; we saw nothing." Over the course of one of the Sun's natural 11-year cycles, there was a weak correlation between cosmic ray intensity and cloud cover - but cosmic ray variability could at the very most explain only a quarter of the changes in cloudiness. And for the following cycle, no correlation was found. Limited effect Dr Svensmark himself was unimpressed by the findings. "Terry Sloan has simply failed to understand how cosmic rays work on clouds," he told BBC News. "He predicts much bigger effects than we would do, as between the equator and the poles, and after solar eruptions; then, because he doesn't see those big effects, he says our story is wrong, when in fact we have plenty of evidence to support it." But another researcher who has worked on the issue, Giles Harrison from Reading University, said the work was important "as it provides an upper limit on the cosmic ray-cloud effect in global satellite cloud data". CLICK ON THE BANNER TO BUY TERRORSTORM IN |
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