Solar influence on climate during the past millennium: Results from transient simulations with the NCAR Climate System Model

Abstract

The potential role of solar variations in modulating recent climate has been debated for many decades and recent papers suggest that solar forcing may be less than previously believed. Because solar variability before the satellite period must be scaled from proxy data, large uncertainty exists about phase and magnitude of the forcing. We used a coupled climate system model to determine whether proxy-based irradiance series are capable U nderstanding and quantifying natural climate variability on decadal to centennial time scales is a prerequisite to project future climate changes. It is important to evaluate comprehensive models in the preindustrial period when natural variations were (relatively) pronounced and anthropogenic influences were comparatively small. The recently improved records of the variations in climate of the past 1,000 years (1) together with solar and volcanic forcing histories (2, 3) provide a key opportunity for (i) evaluating long transient simulations with Atmosphere-Ocean General Circulation Models over the preindustrial era, (ii) for exploring the proposed magnitudes of past solar irradiance changes, and (iii) to estimate natural contributions to century-scale climate variability.

Characteristics of decadal-centennial-scale changes in East Asian summer monsoon circulation and precipitation during the Medieval Warm Period and Little Ice Age and in the present day

“…Its variation is consistent with that of the summer APO index reconstructed from the tree-ring width in Sha County, Fujian Province [36] [37] was used to simulate the longer-term change of the summer APO index over past millennium [38] and the simulated APO was compared with the reconstruction of Zhou et al [30]. The external forcing data used in the model are taken from the reconstructions of Ammann et al [39] and include the effects of solar activity and volcanic eruption on effective solar radiation and greenhouse gases. Moreover, sulfate aerosol changes during 1870-1999 were also taken into account.…”

The Medieval Climate Anomaly and Little Ice Age in Chesapeake Bay and the North Atlantic Ocean

“…Medieval climate was also characterized by hydrometeorological variability across North America (Cook et al, 2007) and Eurasia (Treydte et al, 2006). Solar and volcanic activity (Crowley, 2000;Ammann et al, 2007), solar-oceanic feedbacks (Bond et al, 2001), ocean circulation (Broecker, 2001), Pacific Ocean-atmospheric processes (Cook et al, 2007), and land-use changes Ruddiman, 2007) have all been proposed as factors influencing MCA-LIA climate.…”

A revised 1000 year atmospheric δ13C‐CO2 record from Law Dome and South Pole, Antarctica

“…[3] The record of atmospheric CO 2 concentration extracted from the ice cores drilled at Law Dome (East Antarctica) covering the last 2000 years MacFarling Meure et al, 2006] has been extensively used in modeling studies to constrain the global C cycle of the past [Joos and Bruno, 1998;Trudinger et al, 1999Trudinger et al, , 2005 and its interactions with the climate system [Ammann et al, 2007;Cox and Jones, 2008;Frank et al, 2010]. Models of the global C cycle that include the stable isotopes of C [Joos et al, 1999;Trudinger et al, 2002b;Gerber et al, 2003;Köhler et al, 2006] have found an additional constraint in the companion record of ı 13 C from the same site in Antarctica [Francey et al, 1999, hereinafter F99].…”