EARTH may be heading for a "Little Ice Age", according to scientists at two leading US research institutions.

Researchers from the US National Solar Observatory (NSO) and the Air Force Research Laboratory were considering today whether a decline in solar activity could lead to a period similar to the Maunder Minimum in the 17th century, when there were virtually no sunspots for 70 years.

During this period, known as the Little Ice Age, temperatures dropped and up to 28cm of ice formed in Europe.

New analysis of the Sun's interior, surface and corona showed that the next cycle of sunspot activity "will be greatly reduced or may not happen at all".

Dr Frank Hill, of the NSO's Solar Synoptic Network in Sunspot, New Mexico, 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".

However, Joanna Haigh, professor of atmospheric physics at Imperial College London, said that global warming could reverse a cooling effect.

"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," she said. "When the Sun's activity returns to normal, the greenhouse gases won't have gone away."

