Is a new ‘Little Ice Age’ in store for planet earth?
The Earth could enter a new 'Little Ice Age' in the coming years due to low solar activity, astronomers believe.
Sunspot activity, which follows an 11-year cycle, is due to peak in 2013 after which it will start to wane slightly.
But astronomers think the next upswing will be less intensive than normal, or could fail to happen at all.
That could affect weather on Earth because low solar activity has been linked to low global temperatures in the past.
Between 1645 and 1715 almost no sunspots were observed, a solar period which came to be called the Maunder Minimum.
During those decades Europe suffered frequent unusually harsh winters, and the time was later termed the Little Ice Age.
Although there is no conclusive evidence that one caused the other, many scientists believe it did.
Sunspots are darker patches on the sun's surface, caused by small areas of strong magnetic activity which disrupt the normal flow of intensely heated gases.
Paradoxically when there are most sunspots, overall solar output - called total solar irradiance (TSI) - is also at a high.
Three studies, presented at a meeting of the American Astronomical Society's solar physics division, all point towards declining sunspot activity into the next decade.
Frank Hill, of the National Solar Observatory in New Mexico, who worked on one of the studies, said: "The fact that there are three separate lines of evidence all pointing in the same direction is very compelling."
But Joanna Haigh professor of atmospheric physics at Imperial College London, said global warming could override any cooling effect on the Earth's climate.
She said: "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."
During that time temperatures in north west Europe were about 1C lower than normal, and about 0.5C lower averaged globally.
However, she cautioned: "Even if the predictions are correct, the effect of global warming will outstrip the sun’s ability to cool even in the coldest scenario.
"And in any case, the cooling effect is only ever temporary. When the sun’s activity returns to normal, the greenhouse gases won't have gone away."