As if we needed any more factors to influence our already unpredictable weather, scientists are now concerned about the lack of activity on the sun, which appears to have diminished significantly.
The periodic changes in the sun’s activity, such as changes in levels of solar radiation, coronal mass ejections and solar flares, are known as the solar magnetic activity cycle. These variations, which can affect space weather and the Earth’s climate, have been noted to occur in eleven year cycles for hundreds of years. At this point in the cycle there should be a solar maximum, but space physicists have revealed that,conversely, activity is worryingly low.
""I’ve been a solar physicist for 30 years, and I’ve never seen anything quite like this," commented Richard Harrison, head of space physics at the Rutherford Appleton Laboratory in Oxfordshire, U.K.
The lull has happened very quickly and unexpectedly, and it is not known whether the decline will plateau or continue to fall, but an analysis of ice-cores, accurate long-term indicators of solar activity, suggests that this is the fastest drop seen in the past 10,000 years.
"It’s completely taken me and many other solar scientists by surprise," said Dr Lucie Green, from University College London’s Mullard Space Science Laboratory. "It could mean a very, very inactive star, like the Sun is asleep… a very dormant ball of gas at the centre of our Solar System."
"It’s an unusually rapid decline," agreed Mike Lockwood, professor of space environment physics, from the University of Reading, who believes that the Sun could become even quieter still.
Professor Lockwood has identified 24 separate occasions during the last 10,000 years when the sun has behaved in a similar way, but explained that the present decline is happening faster than any of the previous events. He described how, in the late 20th century, the sun was unusually active and a so called ‘grand maximum’ occurred around 1985, but that since then the sun has become increasingly quiet.
This is not the first time in history that such solar activity has waned, however, as an extremely significant lull occurred in the 17th century. This phase, which saw winters of such intensity that even the Baltic Sea froze over, was known as the Maunder Minimum during which historical records reveal that sunspots virtually disappeared. Astronomers at the time observed less than 50 sunspots, compared to the usual 40,000–50,000 spots noted in modern times.
Temperatures became so cold during this period that even the great River Thames in London froze solid, and Londoners were regularly able to hold markets known as "Frost Fairs" on the ice. The Maunder Minimum spanned from 1645 to about 1715, and occurred in the middle of a phase that came to be known as the "Little Ice Age," during which Europe and North America were subjected to extremely cold winters.
Could we be headed towards another similar period?
Dr. Green thinks this could be the case: "There is a very strong hint that the Sun is acting in the same way now as it did in the run-up to the Maunder Minimum."
Professor Lockwood agrees, and based on his findings he’s raised the risk of a new Maunder Minimum from less than 10% just a few years ago to 25-30%. He believes that we are already beginning to see a change in climate that could ultimately have profound implications for energy policy and transport infrastructure worldwide, particularly in Europe.
"It’s a very active research topic at the present time, but we do think there is a mechanism in Europe where we should expect more cold winters when solar activity is low," he says.
Ultraviolet light radiating from the Sun dips when solar activity is low, resulting in less UV radiation hitting the stratosphere – the second major layer of the Earth’s atmosphere. This then affects the performance of the jet stream, the fast flowing air current that forms a buffer between the icy North and the warmer South, and which has a profound effect on global weather systems.
"These are large meanders in the jet stream, and they’re called blocking events because they block off the normal moist, mild winds we get from the Atlantic, and instead we get cold air being dragged down from the Arctic and from Russia," he says."These are what we call a cold snap… a series of three or four cold snaps in a row adds up to a cold winter. And that’s quite likely what we’ll see as solar activity declines."
The results of this are dominantly felt above Europe, says Prof Lockwood, though there could be implications for a global impact on climate. The recent Intergovernmental Panel on Climate Change concluded with 95% certainty that humans were the "dominant cause" of global warming since the 1950s, predicting that global mean temperatures could rise by as much as 4.8C. The panel suggested that solar variations make only a small contribution to the Earth’s climate, but other opinions suggest that changes in the Sun’s activity could affect the climate and may be overriding the effect of greenhouse gas emissions.
Prof Lockwood believes that the changes we will witness will be more localised, but may still affect the way that we live in different regions:
"If we take all the science that we know relating to how the Sun emits heat and light and how that heat and light powers our climate system, and we look at the climate system globally, the difference that it makes even going back into Maunder Minimum conditions is very small. I’ve done a number of studies that show at the very most it might buy you about five years before you reach a certain global average temperature level. But that’s not to say, on a more regional basis there aren’t changes to the patterns of our weather that we’ll have to get used to."
According to Dr. Green, however, a prolonged sunspot minimum could have a positive effect as solar flares are known to adversely affect radio transmissions and electricity supplies.
"Solar activity drives a whole range of space weather, and these are ultimately effects on the electricity networks, on satellites, on radio communications and GPS on your sat-nav," she explained.
Though random bursts of activity may still occur, calmer periods of space weather would lower the risk to the technological infrastructure that the world is so heavily dependent upon so there could be unexpected benefits, though these may be outweighed by the impact that regular freezing temperatures could have on our road and rail networks.
Ultimately, scientists are not sure what to expect:the sun is not a predictable entity, and all they can do is make predictions based on its previous history of behavior.
"This feels like a period where it’s very strange… but also it stresses that we don’t really understand the star that we live with." says Prof Harrison."Because it’s complicated – it’s a complex beast."
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