Scientists found that a decline in the Sun’s activity did not lead as expected to a cooling of the Earth, a surprise finding that could have repercussions for computer models on climate change.
The Sun’s activity is known to wax and wane over 11-year cycles, which means that in theory the amount of radiation reaching Earth declines during the “waning” phase.
The new study was carried out between 2004 and 2007 during a solar waning phase.
The amount of energy in the ultraviolet part of the energy spectrum fell, the researchers found.
But, contrary to expectation, radiation in the visible part of the energy spectrum increased, rather than declined, which caused a warming effect.
The investigation, based mainly on satellite data, is important because of a debate over how far global warming is attributable to Man or to natural causes.
Climatologists say that warming is overwhelmingly due to man-made greenhouse gases — invisible carbon emissions from coal, gas and coal that linger in the atmosphere and trap solar heat.
But a vocal lobby of sceptics say that this is flawed or alarmist, and point out that Earth has known periods of cooling and warming that are due to variations in the Sun’s output.
“These results are challenging what we thought we knew about the Sun’s effect on our climate,” said lead author Joanna Haigh, a professor at Imperial College London where she is also a member of the Grantham Institute for Climate change.
“However, they only show us a snapshot of the Sun’s activity and its behaviour over the three years of our study could be an anomaly.”
Insisting on caution, Haigh said that if the Sun turned out to have a warming effect during the “waning” part of the cycle, it might also turn out to have a cooling effect during the “waxing” part of the cycle.
In that case, greenhouse gases would be more to blame than thought for the perceptible rise in global temperatures over the past century.
“We cannot jump to any conclusions based on what we have found during this comparatively short period,” Haigh said. “We need to carry out further studies to explore the Sun’s activity, and the patterns that we have uncovered, on longer timescales.”
The study is published in Nature, the weekly British science journal.
We have some further data we can add to this report.
The Sun burns up 400 million tonnes of fuel per second and readings on the Sun’s diameter were taken by the Royal Greenwhich Observatory and also the Maratime Naval College in Washington over a period of 140 years.
The findings which can be seen in the graph below, show that the Sun burns up about 1% of it’s mass every thousand years.
This means that only 10,000 years ago, the Sun would have been 10% bigger than it is today and life on Earth would have been impossible.
In the past, temperatures were warmer than they are today, but our atmosphere was different and worked as a very efficient heat exchanger, radiating excess heat back out into space. As the Sun decreased, so did temperatures until the industrial revolution when the vast quantities of CO2 we pumped into the atmosphere through manufacturing upset the heat exchanging process (The Greenhouse Effect) and temperatures started to rise. This in turn has caused the release of Methane which now puts temperatures in an unstoppable upward spiral.
Climate skeptics who say temperatures were warmer in the past are correct but the reasons for this are given above and our atmosphere could cope. Today this is not the case.
For more information on this subject and to find out what happens next, please download your free copy of The Global Meltdown Domino Effect from this web site.