Solar activity during the last 1000 yr inferred from radionuclide records
Identification of the causes of past climate change requires detailed knowledge of one of the most important natural factors-solar forcing. Prior to the period of direct solar observations, radionuclide abundances in natural archives provide the best-known proxies for changes in solar activity. Here we present two independent reconstructions of changes in solar activity during the last 1000 yr, wh