Geophysical Research Letters - Vol. 26, No. 6


Year 1998 is the warmest in a millennium

Tree rings, varved sediments, ice cores, corals, and historical records can be used to reconstruct climate for the period preceding the instrumental record. Mann et al. [759] reconstruct the Northern Hemisphere mean annual surface temperature and report that the 1990s is likely the warmest decade, with 1998 being the wamest year in at least a millenium. The authors find that the late 11th, late 12th, and late 14th centuries are comparable to mean 20th-century temperature levels. Cooling following the 14th century, in their reconstructed series, marks the initial onset of the Little Ice Age.