Sunspot data vital clue to climate change

Published 22 December 2008

baker.jpgNew discoveries linking periodic changes in the Sun’s magnetic field with global weather patterns could enable scientists to gain a clearer understanding of how additional factors – such as greenhouse gases – contribute to those weather patterns.

A newly-published paper by the University of New England’s Dr Robert Baker establishes the connection between solar cycles and the weather by correlating sunspot activity and rainfall figures for south-eastern Australia over the past 130 years.

Cycles of sunspot activity are a visible indication of the periodic changes in magnetic forces within the Sun. The most well-known sunspot cycle is the 11-year “Schwab” cycle, which comprises alternating five-and-a-half-year periods of relatively high and low sunspot activity.

Dr Baker’s paper, “Exploratory analysis of similarities in solar cycle magnetic phases with Southern Oscillation Index fluctuations in Eastern Australia” (Geographical Research, December 2008), shows that periods of increased sunspot activity are consistently associated with those periods of high rainfall in south-eastern Australia predicted by the Southern Oscillation Index (SOI). Periods of drought, such as that which has afflicted Australia for the past six years, are associated with minimal sunspot activity.

Dr Baker (pictured here) is an Associate Professor in UNE’s School of Behavioural, Cognitive and Social Sciences. His paper compares sunspot / weather patterns in all 23 of the documented “Schwab” cycles, noting particularly the similarity between Cycle 15 (1914-1924) and the current Cycle 23. “Such comparisons between the current cycle and past cycles have important implications for both weather prediction and the monitoring of climate change,” Dr Baker said. “They could not only allow us to forecast farther into the future, but – through analysing differences in weather patterns between the current cycle and a past cycle with similar sunspot activity – they could help us to isolate the effect of recent additions to the system such as greenhouse gases.”

“We have to benchmark the natural system (i.e., the Sun) before looking at additions to it (e.g. carbon dioxide),” he explained. “Comparing current data with those of a century ago can give us an idea of the added effect of greenhouse gases. But sticking your head in the sand and saying the Sun has no effect on climate change is a virtual denial of historical reality.”

“I’m not a ‘climate-change sceptic’,” he added. “But although carbon dioxide could be a major contributor to global warming, it’s just one part of a complex system.” That system is so complex, he said, that the short-term temperature trend in the Southern Hemisphere (since 2002) is actually down rather than up.

Dr Baker is keeping a keen eye on daily reports of solar activity. “The Sun isn’t powering up,” he said. “The period of minimum sunspots signalling the completion of Cycle 23, although due to end in October 2007, is continuing. We could, in fact, be entering a prolonged period of minimal sunspot activity such as the one that brought the ‘Federation droughts’ around the turn of the twentieth century and a dip in global temperatures for a decade.”