October 9, 2011

expert reaction to new research on cold northern European winters during a solar minimum, as published in Nature Geoscience

Researchers showed how changes in solar activity resulted in varying patterns in warm and cold weather during the past winter.

Prof Mike Lockwood FRS, Space Environment Physics Group at the University of Reading, said:

“The Ineson et al paper is really interesting as it shows how variability of the solar heating of the atmosphere at high altitudes (the stratosphere) can influence patterns of weather in the lower atmosphere (the troposphere). This is somewhat surprising because the density of the atmosphere is much lower in the stratosphere than at the Earth’s surface, and we would not expect such effects based on simple energetics.

“Their model shows how solar ultraviolet variations generate mid-latitude wind perturbations in the stratosphere which propagate downwards and intensify via the modulation of planetary wave activity. The authors use input solar UV measurements from the SORCE satellite which have revealed larger changes than were measured by the recently-lost UARS satellite. The SORCE instrument is a new state-of-the-art design and there has been debate that it may somehow have overestimated the UV solar variations: however, recent analysis* of the simultaneously-observed stratospheric ozone densities strongly suggests that this is not the case. The concern is that the SORCE data may have exaggerated the results presented by Ineson et al, but on the other hand, the model does not include those ozone changes which would act to amplify the effect they report.

“The results fit very well indeed with recent observations of regional climate changes that have shown that lower solar activity results in colder winter conditions in Europe – but warmer ones in Greenland, such that there is almost no effect on global mean temperatures. The results give understanding of the associations recently made between cold European winters and low solar activity, and lend support to the idea that they may well become more common in future. However, they have no implications for global warming as the effects in different regions cancel.”

* Climate: Surprises from the Sun, Nature 467:7316, pp696-699, Oct 7 2010.
Solar forcing of winter climate variability in the Northern Hemisphere, Nature Geoscience, DOI: 10.1038/NGEO1282, Oct 9 2011.