Sunspots May Be Sign Of Cooler Temperatures

The Sun may be heading for “hibernation” with a decline in solar activity similar to the Little Ice Age in the 17th century, when frost fairs were held on the frozen Thames, according to scientists at two leading US research institutions.

UNIVERSAL HISTORY ARCHIVE / GETTY IMAGESFairs were held on the frozen Thames in the 18th century during the Little Ice Age

Studies of the Sun’s interior, surface and corona indicate that the frequency of sunspots may fall over the next decade or more, potentially mitigating some of the predicted global warming.

Spot numbers and other solar phenomena rise and fall about every eleven years, but analysis by the US National Solar Observatory and the Air Force Research Laboratory suggests that the next cycle “will be greatly reduced or may not happen at all”.

The scientists are now considering whether this slowdown presages a second “Maunder Minimum” — a 70-year period with virtually no sunspots from 1645 to 1715.

During this period, known as the Little Ice Age, up to 11in (28cm) of ice formed on the Thames for up to two months a year and horse-drawn coaches were ridden along the frozen river from Whitehall to London Bridge.

An extended solar minimum could reduce the global temperature by up to 0.5C for the duration of the slowdown. Some climate sceptics said yesterday that the studies suggested the world had nothing to fear from global warming. However, a small temporary decline in temperature would cancel out only part of the 4C of warming by 2100 predicted by the Intergovernmental Panel on Climate Change if fossil fuels continue to be burnt at the present rate.

Frank Hill, associate director of the NSO’s Solar Synoptic Network, said: “The fact that three completely different views of the Sun point in the same direction is a powerful indicator that the sunspot cycle may be going into hibernation.”

Dr Hill said that his research team had expected to find evidence that the Sun’s next cycle was under way but there had been no sign of it. “This indicates that the start [of the next cycle] may be delayed to 2021 or 2022, or may not happen at all.”

Joanna Haigh, Professor of Atmospheric Physics at Imperial College London, said that changes in solar activity were likely to influence the climate. But she said that the 11-year cycle was only one of the variations in solar activity and needed to be placed in context with longer-term changes.

“This work suggests that the Sun’s activity might be entering a longer period of change — a Grand Minimum, similar to that of the late 17th century,” she said.

“This period is sometimes known as the Little Ice Age, but that is something of a misnomer. First, a real ice age sees huge tracts of land covered in snow and ice year round but that period 300 years ago was nothing like that. Second, while this period led to colder temperatures in northwest Europe, over the entire globe it was less than half a degree cooler than normal.”