http://www.guardian.co.uk/environment/2012/jan/24/sun-changes-global-warming

 

The expected reduction in the Sun's activity will not have a big impact on global temperatures, Met Office research shows

 

A reduction in the Sun's activity is expected this century, but is unlikely to do much to slow global warming due to greenhouse gases, scientists said on Monday.

Research by the Met Office and the University of Reading looked at the most likely changes in the Sun's activity and found that its output was likely to decrease up to 2100, from the "grand maximum" seen in the 20th century.

But this would only cause a reduction in global temperatures of about 0.08C over that time, in comparison to projected rises of 2.5C by 2100 as a result of rising greenhouse gases in the atmosphere.

Even if solar activity fell to levels seen in the so-called Maunder minimum, between 1645 and 1715, when the Sun's output was at its lowest recorded level, the reduction in temperature would only be 0.13C.

The study looked at a range of possible projections of solar activity over the coming century and then applied them to one climate model, taken from the middle of the range of models, to see how it might affect temperatures.

Gareth Jones, climate change detection scientist with the Met Office, said it was important to note the study - due to be published in the Journal of Geophysical Research, Atmospheres - was based on just one climate model.

But he said: "This research shows that the most likely change in the Sun's output will not have a big impact on global temperatures or do much to slow the warming we expect from greenhouse gases."

Peter Stott, of the Met Office, said: "Our findings suggest that a reduction of solar activities to levels not seen in hundreds of years would be insufficient to offset the dominant influence of greenhouse gases on global temperatures in the 21st century."

Prof Mike Lockwood, expert in solar studies at the University of Reading said: "The 11-year solar cycle of waxing and waning sunspot numbers is perhaps the best-known way the Sun changes, but longer-term changes in its brightness are more important for possible influences on climate."

He said it was most likely the Sun's activity would drop to the levels of the Dalton minimum around 1820.

The probability of solar output falling to the levels seen in the Maunder minimum, or returning to the high activity of the 20th century, was just 8%.