Northern Hemisphere Temperatures During the Past Millennium: Inferences, Uncertainties, and Limitations

M.E. Mann, R.S. Bradley, M.K. Hughes
Department of Geosciences, Morrill Science Building, University of Massachusetts, Amherst MA 01003-5820, USA


Building on recent studies, we attempt hemispheric temperature reconstructions with proxy data networks for the past millennium. We focus not just on the reconstructions, but the uncertainties therein, and important caveats. Though expanded uncertainties prevent decisive conclusions for the period prior to AD 1400, our results suggest that the latter 20th century is anomalous in the context of at least the past millennium. The 1990s was the warmest decade, and 1998 the warmest year, at moderately high levels of confidence. The 20th century warming counters a millennial-scale cooling trend which is consistent with long-term astronomical forcing.

AGU Index Terms: 1620 Climate dynamics; 3344 Paleoclimatology; 3309 Climatology; 4267 Paleoceanography
Keywords/Free Terms: Climate Change, Global warming, Paleoclimate reconstruction, Climate proxy data

Geophysical Res. Ltrs. 1999GL900070
Vol. 26 , No. 6 , p. 759

© 1998 AGU