Sun throws new light on global warming

Financial Times:

The sun has been behaving more curiously in the last few years than previously thought, scientists have found, in research that throws new light on global warming.

Data from new satellites show that although the sun’s activity – which can be measured in part by observing sunspots – has been at an unusual low, the effect of this has not been to cool the earth, as might have been expected, but to warm it.

The research challenges some accepted opinions on the effect of the sun’s activities on the climate, as it suggests that climate models may have slightly over-estimated the sun’s role in warming the earth.

Scientists from Imperial College London and the University of Colorado monitored the sun’s activity from 2004-07, a period when its activity was declining. Activity on the sun waxes and wanes over an 11-year cycle, and in the declining phase the overall amount of radiation reaching the earth also declines.

That should have meant that the earth would become slightly cooler. But instead, the amount of energy reaching the earth increased.

This has led the scientists involved to theorise that, conversely, decreasing solar activity could slightly warm the earth.

Joannah Haigh, professor at Imperial and lead author of the study, said: “These results are challenging what we thought we knew about the sun’s effect on our climate. If further studies find the same pattern over a longer period, this could suggest we may have overestimated the sun’s role in warming the planet, rather than underestimating it.”

However, the amount of warming involved either way is very small.

The research, published on Thursday in the peer-review journal Nature, is complex, and the authors cautioned that there were several potential explanations for their observations. They also warned that as the research had been carried out over a relatively short period, it would be wrong to extrapolate too much from it, and that more study was needed.

However, the research is likely to spark further debates in climate circles. The role of the sun has been hotly disputed, with some sceptics claiming that solar activity, measured by sunspots, was the real culprit behind warming temperatures.

Prof Haigh said: “This [new research] does not give comfort to climate change sceptics at all – it may suggest we do not know enough about the sun but casts no aspersions on climate models [which] would still be producing the same results without these solar effects.”