What follows is the press release by GEOMAR on the very recent Muscheler et al paper showing the sun’s profound impact on northern hemispheric climate. Other sites touched on this paper, here and here.
Now I’ve translated the entire GEOMAR press release from the German. The results of the study are impressive:
Irregularities in solar activity impacted the climate 20,000 years ago.
04 Sept 2014/Kiel. In a model study, climate scientists of the GEOMAR Helmholtz Center for Ocean Research in Kiel reconstructed the relationship between solar activity and climate during the last ice age. With their climate-chemical model, they were able to make a considerable contribution to a study by the Swedish Lund University published in the international journal Nature Geoscience.
A known pattern of behavior of the sun is its irregular solar activity. The most well-known activity cycle is the 11-year sunspot cycle where every 11 years there is a switch between sunspot maximum and sunspot minimum. There are also other known fluctuations of other timescales. Sunspots are places on the sun’s surface that appear to be darker because the solar radiation is emitted into the universe with reduced strength. At the same time high energy radiation, foremost in the UV range, leaves the sun. During a sunspot minimum there are fewer sunspots and thus less energy-intensive radiation reaching the earth. When sunspots reach maximum activity, precisely the opposite is true.
More solar radiation, particularly in the UV range, during a sunspot maximum leads to a warming of the stratosphere (between 15 – 50 km) in the tropics and lead to an increased ozone production. Through complicated interactive mechanisms this in turn leads to atmospheric circulation changes which are perceived at the earth’s surface. The mechanisms on how changes in solar activity impact the atmosphere are still the subject of ongoing research. There is especially much speculation on the relationship between large sunspot minima and cold, snowy winters or on whether the current low sunspot activity might be responsible for the pause in global warming.
Scientists of Lund University (Sweden), in cooperation with GEOMAR climate scientists Prof. Dr. Katja Matthes and Dr. Rémi Thiéblemont, have succeeded in reconstructing solar activity back in the last ice age. The study was published in August in the international journal of Nature Geoscience.
Ice cores from Greenland were used to get information on solar activity for that period, a time when Sweden and North Germany were under a thick sheet of ice. The evaluation principle works in a similar manner as with tree-rings: The ice cores contain many layers from which information on temperature and precipitation conditions can be derived. The radioactive, cosmic molecules of beryllium and carbon play an important role here. Namely they are created in the atmosphere when the solar magmatic field around the earth is weak and thus allow lots of cosmic radiation to come through. When the ice core contains lots of radioactive beryllium and carbon, it means there was a weak protective shield, and so indicates weak solar activity.
A combined analysis of ice cores and dripstones allowed the scientists of Lund University to reconstruct solar activity until the end of the last ice age. It shows that the 11-year sunspot cycle also existed at the time, displaying a typical pattern of solar activity. “First of all we have succeeded in producing a high resolution record of solar activity,” says Prof. Matthes. “With our climate model, which transfers the solar signal from the stratosphere to the earth’s surface more accurately than other models, we were able to reconstruct typical atmospheric circulation patterns for a solar minimum, thus enabling us to infer possible temperature and precipitation patterns over Greenland that correspond very closely to the conditions at the end of the last ice age. The agreement is impressive and allows us to suspect that the mechanism for influence on climate by solar activity back then and today function very similarly.”
The results confirm the evidence from other studies showing years with low solar activity are associated with harsh winters over the Northern Hemisphere. One example are the strong winter outbreaks connected with snowfall and storms, as experienced in 2008 and 2010 in North Europe and North America. During these years we found ourselves in a sunspot minima.
“The effect of solar activity on regional climate fluctuations is very revealing. Estimations of future solar activity could lead to more precise climate forecasts over the next deacades,” explains Prof. Matthes.
Study done by:
Adolphi, F., R. Muscheler, A. Svensson, A. Aldahan, G. Possnert, J. Beer, J. Sjolte, S. Björck, K. Matthes, R. Thiéblemont (2014): Persistent link between solar activity and Greenland climate during the Last Glacial Maximum, Nature Geoscience, http://dx.doi.org/10.1038/NGEO2225
This ice core was extracted in Greenland as part of the National Ice Sheet Project of the National Science Foundation. It comes from a depth of 1837-1838 Metern and provides a record of the climate of the last thousands of years. Photo: USGS via Wikimedia Commons.