Raimund Muscheler

Large changes in solar ultraviolet radiation can indirectly affect climate(1) by inducing atmospheric changes. Specifically, it has been suggested that centennial-scale climate variability during the Holocene epoch was controlled by the Sun(2,3). 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 Be-10 accumulation, a proxy for solar activity, from 3,300 to 2,000 years before present. We find a sharp increase in windiness and cosmogenic Be-10 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.