London: There could be sharp decline in global warming by 2022, as scientists claim to have unearthed evidence that the sun is poised to enter its first period of "hibernation" since the Little Ice Age of the early 1700s.

The sun goes through a regular cycle of activity that peaks every 11 years. During its most frenzied periods, huge magnetic storms erupt from the sun while vast sunspots appear on its surface, but during the quiet part of the cycle -- called the solar minimum -- eruptions and sunspots are rarer.

If the new claims are right, global warming caused by greenhouse gases could be less severe over the next few decades than predicted, a news daily reported.

Astronomers believe the sun should now be building up to its next maximum and that sunspots should be appearing on its surface.

But, three separate studies, presented at an astronomy conference in America this week, have found clues that the sun is not waking up on schedule.

Dr Frank Hill of America's National Solar Observatory showed that a regular jet-stream current within the sun, which was due in 2008 and 2009, has failed to start up again.

Meanwhile, Dr Richard Altrock, of Sacramento Peak Observatory, who has been studying the sun's "atmosphere" (the corona) for 40 years, found that a tell-tale march of magnetic activity towards the poles that heralds the start of the solar maximum has failed to materialise.

And Matthew Penn, also from the National Solar Observatory, has shown that the strength of the magnetic field inside sunspots has been much weaker than expected and is in steady decline.

If this continues, the sun will have lost its spots completely by 2022. 

The last time the sun went quiet was during the "Maunder Minimum" from 1645 to 1715, when Europe and America suffered a succession of bitterly cold winters called the Little Ice Age.

The Thames, which was wider and slower in those days, regularly froze over, while sea ice choked the coasts of England.

Mike Lockwood, professor of space environment physics at the University of Reading, said: "Our research shows there is an eight per cent chance that we will return to Maunder Minimum conditions over the next 40 years.

"But, given the observed and predicted rise in greenhouse gases, we find it would do no more than slow global warming a little."

However, Joanna Haigh, professor of atmospheric physics at Imperial College London, said: "In a future grand minimum, the sun might again cool the planet by up to one degree. Greenhouse gases, on the other hand, are expected to raise global temperatures by between 1.5C and 4.5C by 2100.

"So even if the predictions are correct, global warming will outstrip the sun’s ability to cool."