David Whitehouse: Will Inactive Sun Cause Global Cooling?
Something is happening to our sun. It has to do with sunspots or rather the activity cycle their coming and going signifies. Sunspots – dark magnetic blotches on the sun’s surface – come and go in an 11-year cycle of activity first noticed in 1843. It is a process related to the motion of superhot, electrically charged gas inside the sun; a kind of internal conveyor belt where vast sub-surface rivers of gas take 40 years to circulate from the equator to the poles and back.

Somehow, in a way not very well understood, this circulation produces the sunspot cycle in which every 11 years there is a sunspot maximum followed by a minimum. In the last century, the sun’s activity may have been the highest for more than 8,000 years with lots of strong solar cycles. But then things turned. The recent cycle – so called ‘Cycle 24′ – is puny. If history is anything to go by, then the sun’s change of mood could affect us all by cooling the earth and throwing our climate change calculations into disarray....

...But there was something strange about the time when the sunspots disappeared that left scientists to ponder if the sun’s unusual behaviour could have something to do with the fact that the 17th century was also a time when the earth’s northern hemisphere chilled with devastating consequences.

Scientists call that event the Little Ice Age and it affected Europe at just the wrong time. In response to the more benign climate of the earlier medieval warm period, Europe’s population may have doubled. But in the mid-17th century, demographic growth stopped and in some areas fell – in part due to the reduced crop yields caused by climate change. Bread prices doubled and then quintupled and hunger weakened the population....