Isolating a Solar Fingerprint in Climate of the Last Millennium

Caspar Ammann [ammann@ucar.edu], National Center for Atmospheric Research, Boulder, Colorado; Hee-Seok Oh, Seoul National University, South Korea; Fortunat Joos, University of Bern, Switzerland; Philippe Naveau, Centre National de Recherche Scientifique, Paris, France; and Eugene Wahl, Alfred University, New York.

The effect of the Sun on climate of the past centuries and millennia has long been used to explain climatic changes in both mean and extremes. However, recent detection studies focused on the latest reconstructions of pre-industrial climate have found no clear evidence of a strong solar influence but rather identified explosive volcanism as the prime forcing. Even the small variations of greenhouse gases prior to the industrial revolution have been found to show a stronger relation to climate than solar activity. Here, we revisit the potential role of the sun in centennial time scale climate variability. A clear solar fingerprint in terrestrial climate is found in both real world climate reconstructions and output from coupled Atmosphere-Ocean General Circulations Model simulations that were forced with various estimates of solar irradiance change. The common signals as well as differences are discussed with regard to potential reconstruction biases, model limitations and internal climate variability.