Holocene climatic change, 14 C wiggles and variations in solar irradiance

Abstract

Evidence from the advances and retreats of alpine glaciers during the Holocene suggests that there were at least 14 century-timescale cool periods similar to the recent Little Ice Age. Here, we examine the hypothesis that these cool periods were caused by reductions in solar irradiance. A statistically significant correlation is found between the global glacial advance and retreat chronology of Röthlisberger and variations in atmospheric 14 C concentration. A simple energy-balance climate model is used to show that the mean reduction of solar irradiance during times of maximum 14 C anomaly like the Maunder Minimum would have to have been between 0.22 and 0.55 % to have caused these cool periods. If a similar solar irradiance perturbation began early in the 21st century, the associated climate effects would be noticeable, but still considerably less than those expected to result from future greenhouse gas concentration increases.