Boffins confirm sunspot-weather link
Sunspots still don’t account for climate change
A group of scientists led by German researcher Frank Sirocko of the Johannes Gutenberg University at Mainz has provided a long-term statistical study relating weather to the Sun’s 11-year cycle.
The study, carried out in conjunction with the Institute for Atmospheric and Climate Science in Zurich, Switzerland, used records of freezes in the Rhine dating back to 1780 to correlate conditions on the river to the sunspot cycle.
The researchers chose the Rhine because, as they put it, freezing is an “on-off” event for the major waterway. “Either there is ice or there is no ice,” the professor of Sedimentology and Paleoclimatology explained.
Because the Rhine was used for river transport from the early 19th century through to the 20th, cargo docks maintained records of freezing events, the researchers say. These documents showed that ten of the 14 documented freezes occurred during periods of low sunspot activity. Further statistical analysis suggests that a low sunspot period leads to a 99 percent chance of a cold winter in Central Europe.
Sirocko says the study provides the first “statistically robust evidence that the succession of cold winters during the last 230 years in Central Europe has a common cause”.
However, the research doesn’t invalidate carbon-driven warming. Co-author of the study Stephan Pfahl explains that the sunspot cycle “does not impact hemispherically averaged temperatures, but only leads to regional temperature anomalies”.
Rather, solar activity is merely added to the list of climate-impacting variables, Sirocko said. The same study also suggests that even the colder “low-sunspot” winters are growing warmer, with the researchers pointing out that the Rhine hasn’t frozen over since 1963 (in spite of record-setting cold winters in 2010 and 2011).
The study is published in Geophysical Research Letters, and the announcement from the American Geophysical Union is here. ®