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Science/Tech See other Science/Tech Articles Title: Cooling Sun brings relief to sweltering Earth Help in battle against global warming as scientists claim that our nearest star is about to go into a period of reduced activity Robin McKie, science editor The earth could be rescued from global warming by an unlikely saviour: not fewer cars, nor less pollution, nor even thousands of wind farms spread across Britain's hillsides - but, remarkably, by a cooler Sun. An international group of scientists believes a period of reduced solar activity could soon bring desperately needed cooling to our sweltering world. The work is based on research of past periods of climatic change, including the Little Ice Age in the 1700s when Europe shivered, the Thames froze over, and harvests failed. At the same time, solar activity dropped and sunspots disappeared from the face of the Sun. Now leading scientists are predicting that we may soon enter such a period again - although they stress such cooling would only bring temporary relief to our overheated world. In the end, the Earth will still be swamped by huge rises in global temperatures, triggered by human activities, that will affect the planet over the next few decades. 'If there was a period of low solar activity, it could give us a little more time to combat global warming and to introduce the curbs on the carbon emissions that we need to limit climate change,' said Professor Joanna Haigh, of Imperial College, London. The revelation comes in the wake of Nasa's successful launch on Friday of the Solar-B mission, which will study the Sun's corona. Space scientists are finalising preparations for two other probes to study the star that dominates the world: Stereo, in which one spaceship will fly ahead of, and another behind, the Earth as it orbits the Sun; and Solar Orbiter, which will swoop close to the Sun's surface to gain a detailed view of its surface. Scientists have known for decades that the Sun's output varies over an 11-year cycle. More recently, they have found what appear to be other, longer cycles affecting its output. These occasionally cause perceptible drops in solar radiation. For example, during the Little Ice Age, which affected Europe from 1650 to the end of the 18th century, astronomers noted that sunspots disappeared completely from the face of the Sun. 'High numbers of sunspots are associated with increased solar output,' said Professor Sami Solanki, of the Max Planck Institute for Solar Research, in Katlenberg-Lindau, Germany. 'Sunspots occur when magnetic fields rip through the Sun's surface and show that vast amounts of energy are being released deep within its heart. The impact on the Earth can be considerable.' Studies have shown that when solar output is high, the climate tends to be hot. For example, over the past 30 to 40 years scientists believe the Sun has been particularly active, adding to Earth's already considerable heating problems. However, things may change in the near future. One study, by a group led by solar expert Leif Svalgaard of ETK - a consulting firm based in Houston, Texas - has predicted that in the next few years solar activity is set to drop to its weakest level in over a century, with sunspot numbers declining by about 40 per cent over the next decade. 'Sunspot numbers will be extremely small,' he said. This point was backed by Cambridge solar physicist Nigel Weiss. 'Periods of high solar activity do not last long, perhaps 50 to 100 years, then you get a crash,' he told New Scientist. 'It is a boom-bust system and I would expect a crash soon.' The net result of this sunspot decrease could be to lead to an increase in cloud formation and also to a reduction in ultra-violet radiation reaching the atmosphere. Overall, it would bring about a 0.2C decline in global temperatures, according to Solanki and his colleagues. That is only a tenth of the rise now predicted to grip the world over the next few decades, however. Not enough to save the Earth from a sweltering, overheated fate but possibly enough to provide a little breathing space in which humanity could take remedial action. 'Just who might benefit most from any reduction in solar energy is hard to say at present,' added Professor Haigh. 'The Little Ice Age was mainly felt in western Europe and the rest of the world was relatively unaffected - possibly because meteorological effects cause solar radiation reductions to have localised impacts. That could happen again, though it is difficult to predict where.' However, not every expert on solar radiation agrees with the idea that sunspot numbers are set to decline. Other scientists - using the same data - have come to a different conclusion. They predict that numbers will increase over the next decade. 'We predict a 30 to 50 per cent increase,' said Mausumi Dikpati, of the National Centre for Atmospheric Research's High Altitude Observatory in Boulder, Colorado. If such an increase occurs, there could then be a strengthening of global temperature rises. It is an interesting issue, admits Svalgaard, one of the main backers of the low-sunspot school. 'If all models predict the same thing, we don't get wiser.' As to finding out who is right, that would take a couple of years, he added. 'We're all waiting.' Great ball of fire The Sun is a sphere of super-hot gas, 870,000 miles in diameter. Its volume is great enough to hold more than one million Earths. The surface temperature is 5,500 degrees Centigrade: it is 15 million degrees C at its core. The average distance from Earth to Sun is 93 million miles. At a steady 70mph, it would take 152 years to drive there. Even with a speed of 186,000 miles per second, it takes light eight-and-a-half minutes to travel from the Sun's surface to the Earth. At 4.5 billion years old, the Sun is halfway through its lifespan. George Harrison's Here Comes the Sun was written in Eric Clapton's garden in 1969. Members of the http://georgeharrison.com forum voted it their favourite track.
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