Solar irradiance during the last 1200 years based on cosmogenic nuclides |
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| Authors: | EDOUARD BARD GRANT RAISBECK FRANÇOISE YIOU JEAN JOUZEL |
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| Institution: | CEREGE, Universitéd'Aix‐Marseille, UMR‐CNRS 6635, Europöle de l'Arbois, BP 80, 13545 Aix‐en‐Provence Cedex 4, France;;Centre de Spectrométrie Nucléaire et de Spectrométrie de Masse, IN2P3‐CNRS, 91405 Orsay, France;;Laboratoire des Sciences du Climat et de l'Environnement, CEA‐CNRS, Orme des Merisiers, 91191 Gif‐sur‐Yvette cdx, France |
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| Abstract: | Based on a quantitative study of the common fluctuations of 14C and 10Be production rates, we have derived a time series of the solar magnetic variability over the last 1200 years. This record is converted into irradiance variations by linear scaling based on previous studies of sun‐like stars and of the sun's behavior over the last few centuries. The new solar irradiance record exhibits low values during the well‐known solar minima centered at about 1900, 1810 (Dalton) and 1690 ad (Maunder). Further back in time, a rather long period between 1450 and 1750 ad is characterized by low irradiance values. A shorter period is centered at about 1200 ad , with irradiance slightly higher or similar to present day values. It is tempting to correlate these periods with the so‐called "little ice age" and "medieval warm period", respectively. An accurate quantification of the climatic impact of this new irradiance record requires the use of coupled atmosphere–ocean general circulation models (GCMs). Nevertheless, our record is already compatible with a global cooling of about 0.5‐1°C during the "little ice age", and with a general cooling trend during the past millenium followed by global warming during the 20th century (Mann et al., 1999). |
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