This is interesting. A quick cooling in Europe together with an increase in humidity and particularly in windiness was found to coincide with a long-term reduction in solar activity 2800 years ago during something called the “Homeric minimum”.
The paper published in Nature Geoscience suggests that solar grand minima was the trigger for cooling of the climate in Europe. Approximately 2800 years ago, one of these Grand Solar Minima, the Homeric Minimum, caused a distinct climatic change in less than a decade in Western Europe. While they talk about UV, the forcing mechanisms still are unclear but the evidence in this paper suggests that solar effects are significant. Dr. Leif Svalgaard sent me the notice of the paper, and included this graph which he says:
Attached is one of the better reconstruction of solar activity.
There are, of course, several other excursions not mentioned, e.g. the more severe one around 650 AD
Here’s the abstract, bold mine:
Regional atmospheric circulation shifts induced by a grand solar minimum
by Celia Martin-Puertas, Katja Matthes, Achim Brauer, Raimund Muscheler, Felicitas Hansen, Christof Petrick, Ala Aldahan, Göran Possnert & Bas van Geel
Large changes in solar ultraviolet radiation can indirectly affect climate1 by inducing atmospheric changes. Specifically, it has been suggested that centennial-scale climate variability during the Holocene epoch was controlled by the Sun2, 3. However, the amplitude of solar forcing is small when compared with the climatic effects and, without reliable data sets, it is unclear which feedback mechanisms could have amplified the forcing. Here we analyse annually laminated sediments of Lake Meerfelder Maar, Germany, to derive variations in wind strength and the rate of 10Be accumulation, a proxy for solar activity, from 3,300 to 2,000 years before present. We find a sharp increase in windiness and cosmogenic 10Be deposition 2,759 ± 39 varve years before present and a reduction in both entities 199 ± 9 annual layers later. We infer that the atmospheric circulation reacted abruptly and in phase with the solar minimum. A shift in atmospheric circulation in response to changes in solar activity is broadly consistent with atmospheric circulation patterns in long-term climate model simulations, and in reanalysis data that assimilate observations from recent solar minima into a climate model. We conclude that changes in atmospheric circulation amplified the solar signal and caused abrupt climate change about 2,800 years ago, coincident with a grand solar minimum.
UPDATE: Here’s the press release from the Helmholtz Association of German Research Centres.
Climatic effects of a solar minimum
A grand solar minimum and the climate response recorded for the first time in the same climate archive highlights the need for a more differentiated approach to solar radiation
An abrupt cooling in Europe together with an increase in humidity and particularly in windiness coincided with a sustained reduction in solar activity 2800 years ago. Scientists from the German Research Centre for Geosciences GFZ in collaboration with Swedish and Dutch colleagues provide evidence for a direct solar-climate linkage on centennial timescales. Using the most modern methodological approach, they analysed sediments from Lake Meerfelder Maar, a maar lake in the Eifel/Germany, to determine annual variations in climate proxies and solar activity.
The study published online this week in Nature Geosience (06/05/2012) reports the climatic change that occurred at the beginning of the pre-Roman Iron Age and demonstrates that especially the so-called Grand Minima of solar activity can affect climate conditions in western Europe through changes in regional atmospheric circulation pattern. Around 2800 years ago, one of these Grand Solar Minima, the Homeric Minimum, caused a distinct climatic change in less than a decade in Western Europe.
The exceptional seasonally laminated sediments from the studied maar lake allow a precise dating even of short-term climate changes. The results show for a 200 year long period strongly increased springtime winds during a period of cool and wet climate in Europe. In combination with model studies they suggest a mechanism that can explain the relation between a weak sun and climate change. “The change and strengthening of the tropospheric wind systems likely is related to stratospheric processes which in turn are affected by the ultraviolet radiation” explains Achim Brauer (GFZ), the initiator of the study. “This complex chain of processes thus acts as a positive feedback mechanism that could explain why assumingly too small variations in solar activity have caused regional climate changes.”
Albeit those findings cannot be directly transferred to future projections because the current climate is additionally affected by anthropogenic forcing, they provide clear evidence for still poorly understood aspects of the climate system, emphasizes Achim Brauer. In particular, further investigations are required with a focus on the climatic consequences of changes in different wavelengths of the solar spectrum. Only when the mechanisms of solar-climate links are better understood a reliable estimate of the potential effects of the next Grand solar minimum in a world of anthropogenic climate change will be possible. In this respect, well-dated annually laminated lake sediments are also in future of crucial importance for these studies.
Therefore, scientists from the German Research Centre for Geosciences (GFZ) and other institutions search for such archives around the world in order to to obtain a more accurate approach to the solar-climate relationship and the different regional responses.
Celia Martin-Puertas, Katja Matthes, Achim Brauer, Raimund Muscheler, Felicitas Hansen, Christof Petrick, Ala Aldahan, Göran Possnert and Bas van Geel: “Regional atmospheric circulation shifts induced by a grand solar minimum”, Nature Geoscience, DOI 10.1038/NGEO1460
Pictures of Eifel maar lakes and drilling can be found here: