Temperatures in the past millennium

Abstract

Historic proxy studies have distinguished two periods of particular interest in the past millennium. One is the putative Medieval Warm Period (MWP) centered near 900–1000, that was supposedly an unusually mild climate. The other was the Little Ice Age (LIA) from perhaps 1400 (or 1600) to about 1850 when temperatures were unusually cold. The nature of proxies is such that a considerable amount of variability in results derives from various proxies even if the underlying data are uniform spatially and temporally. Compounding this is the fact that, apparently, the MWP and LIA represented trends that varied spatially and temporally, so the net result of proxy measurements for these periods is typically not clear-cut.