Whence the Little Ice Age?

摘要

In the second half of the past millennium, glaciers advanced and temperatures fell in many regions around the world, although the timings and durations of the cold spells differed widely between regions. Numerous causes for this Little Ice Age have been proposed, including cyclical reductions in solar irradiance, changes in ocean circulation, and increases in volcanic activity, but the direct radiative effects of these processes are either weak or short-lived and require substantial feedbacks within the climate system. Miller ef al. now exploit the fact that small ice caps in Arctic Canada are retreating, exposing vegetation that was entombed when the ice caps were advanc- ing. By radiocarbon-dating these plants, the authors can accurately determine the time of glacial advance.