This year will be remembered for many milestones, such as the record performances at the Beijing Olympics and a historic US presidential race. Less noticed, but perhaps just as significant in the history of our solar system, for the first time in 95 years, a month has gone by without a single spot forming on the sun's surface. While this may appear to interest only scientists who rarely leave their laboratories, the level of solar activity has an impact on climate conditions that affect everyone on the planet. Indeed, the absence of sunspots has caused commentators to revisit an unpublished paper from 2005 by a pair of astronomers from the National Solar Observatory in Arizona.
Dr William Livingston and Matthew Penn predicted that, by 2015, sunspots would vanish for ever, stoking fears that a mini ice age would be in store, severely impacting life on parts of the globe. If this is the case, it will not be the first time a lack of sunspots has been linked to cooler temperatures. In the second half of the 17th and the early 18th century, few sunspots were recorded - there were 50 when one thousand times that number would have been expected. The weather was so cold the River Thames in London froze over for weeks and harvests throughout Europe failed, all because of the unpredictable behaviour of a star almost two hundred million kilometres away from Earth.
A sunspot is an area of intense magnetic activity and lower temperatures on the sun's surface - lower by the sun's standards, that is. Instead of being around 5,800 C, like the rest of the sun, these areas have temperatures between 4,000 C and 4,500 C. While sunspots may be cooler themselves, they lead to greater solar heating because the areas around them are extra hot. If there are no sunspots, then the magnetic field of the sun is weakened and solar heating is minimised.
Scientists believe this magnetic field changes with time because of the rotation of the sun and the turbulence this brings with it. If we are entering a cold phase, it will represent a major turnaround; just four years ago, headlines were revealing than sunspot activity was at a 1,000-year peak. According to Professor Sami Solanki, director of the Max Planck Institute for Solar System Research in Germany, the past 50 to 60 years have had "a major high" in sunspot numbers.
"If you look back at the last 10,000 years there's been another 20 periods where the sun has been particularly active," he says. Generally, the number of sunspots rises and declines in an 11-year cycle that results from the way rivers of gases circulate between the poles and the equator of the sun. "Every 10 or 11 years you have a period with many sunspots and a period with very few," Prof Solanki says.
He believes what we are seeing at the moment is not unusual for the low point in this cycle, but views among researchers vary wildly. There is, as Prof Solanki puts it, "no consensus whatsoever," with opinions varying according to the details of the mathematical models used for projections. Some groups of researchers believe the sun will be very weak, others believe it will be particularly strong. "I don't think at the moment you can make any reliable predictions. It is very difficult because it's a very chaotic phenomenon. We don't have any physical insight to make a proper job of it," he says.
It will take a few years for us to know which view turns out to be right. In the meantime scientists will be anxiously scanning the surface of the sun to see small sunspots at high latitude, which would herald the start of a new cycle of solar activity. There is little sign of them so far. Even if those who predict less solar activity turn out to be right, the consequences may not be too severe. Current thinking, Prof Solanki explains, is that variations in solar activity cause temperatures to increase or decrease by only about 0.2 or 0.4 C. If this is compared to the estimated change in temperatures brought about over the past century by climate change due to man's activities - a 0.8 C increase according to some reports - then the impact of spikes and dips in the power of the sun, while not negligible, will not be catastrophic.
When matched against some dire predictions about an increase in world temperatures from global warming of up to 4C by the end of the 21st century, a few decades of solar downtime has less significance. But this year, as the sun has calmed down, temperatures appear to have cooled down. Over the past 18 months the average global temperature has cooled to what it averaged a century ago, before there were fears about global warming. "The last time there were no sunspots and there was a mini ice age in the 17th century, there were no greenhouse gases. Even if we had a less bright sun now, I would be surprised if we had a little ice age. I am not sure that, in Abu Dhabi, a little ice age would be felt at all," Prof Solanki says. However, just as there is no consensus on whether the sun is about to enter a cooler period, scientists cannot agree on how much impact a cooler sun could have. The decrease could be as much as 1.5 C over the next 12 years, according to some members of the Russian Academy of Sciences. And this may be more than enough to counteract the impact of global warming. Even if the spots on its surface do not cause us problems over the coming years, the sun is likely to make conditions on earth far less hospitable in the more distant future. Today's hot UAE summer will seem like a cool spring day. As part of a cycle of stellar evolution lasting more than 10 billion years, the sun is gradually growing larger and over the next billion years, is likely to increase in size by several per cent. "A few per cent is a lot. It will have a marked effect. There are predictions we'll see a runaway greenhouse effect due to the brightness of the sun in one billion or two billion years. That would be a time to worry," says Prof Solanki. In a billion years' time, it is thought the Earth's surface will be too hot for water to exist as a liquid and the planet will be uninhabitable. So the sun, the planet that sustains life, could turn out to be our biggest enemy. Consider yourself warned - and don't forget your sunblock. dbardsley@thenational.ae
