Google search basis undermines sunspot-winter coldness link

Franck Sirocko's 2012 study incorrectly dated this 1929 postcard identifying a year that the Rhine froze as being from 1963, which is one of many problems Geert Jan van Oldenborgh and his colleagues found with it. Image from van Oldenborgh et al, used under Creative Commons license, see citation below.

Franck Sirocko’s 2012 study incorrectly dated this 1929 postcard identifying a year that the Rhine froze as being from 1963, which is one of many problems Geert Jan van Oldenborgh and his colleagues found with it. Image from van Oldenborgh et al, used under Creative Commons license, see citation below.

European researchers have strongly criticised a recent study linking cold winters in the continent to cycles affecting the sun for relying on a shallow internet search. In August 2012, Franck Sirocko at University of Mainz, Germany, and his teammates linked cold years to sunspot activity lows using historical reports of when the river Rhine froze. But their results disagree with previous research, and previously unpublished findings from Geert Jan van Oldenborgh from KNMI, the Royal Netherlands Meteorological Institute, in De Bilt. And when Geert Jan looked into why this was, he found problems common in research on this topic over 50 years ago, updated for the internet age.

“These problems are fundamental – all the results that they claimed are spurious,” Geert Jan told me. “It is simply an incorrect paper. Usually incorrect results are just ignored, they do not get cited much and are quickly forgotten. However, this time we took the unusual step to write a comment on the paper. This decision was based on the low quality and the wide publicity it was given.”

That publicity came largely because the American Geophysical Union, which published the 2012 paper, put out a press release about it that the media reported widely. It tells how Franck’s team used historical documents to find that the Rhine froze in multiple places fourteen different times between 1780 and 1963. 10 of the 14 freeze years occurred close to the point in an 11 year cycle when there are fewest sunspots. “We provide, for the first time, statistically robust evidence that the succession of cold winters during the last 230 years in Central Europe has a common cause,” Franck said in the press release.

Sunspot cycles had been linked to weather throughout the 19th and 20th centuries, until Barrie Pittock started going over the evidence in the 1970s. Barrie, who led the Climate Impact Group at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Australia until his retirement in 1999, found no link beyond day-to-day weather effects. He also found many studies had used bad or incomplete data to say otherwise. Read the rest of this entry »