1. Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden
2. Dynamical-Stochastical Laboratory, Hydrometeorological Research Centre of Russia, Bolshoy Predtechensky Lane 11/13, Moscow 123 242, Russia
3. Department of Physical Geography and Quaternary Geology, Stockholm University, SE-106 91 Stockholm, Sweden

Correspondence to: Anders Moberg¹ Correspondence and requests for materials should be addressed to A.M. (Email: anders.moberg@misu.su.se).

Abstract

A number of reconstructions of millennial-scale climate variability have been carried out in order to understand patterns of natural climate variability, on decade to century timescales, and the role of anthropogenic forcing^{1, 2, 3, 4, 5, 6, 7, 8}. These reconstructions have mainly used tree-ring data and other data sets of annual to decadal resolution. Lake and ocean sediments have a lower time resolution, but provide climate information at multicentennial timescales that may not be captured by tree-ring data^{9, 10}. Here we reconstruct Northern Hemisphere temperatures for the past 2,000 years by combining low-resolution proxies with tree-ring data, using a wavelet transform technique¹¹ to achieve timescale-dependent processing of the data. Our reconstruction shows larger multicentennial variability than most previous multi-proxy reconstructions^{1, 2, 3, 4, 7}, but agrees well with temperatures reconstructed from borehole measurements¹² and with temperatures obtained with a general circulation model^{13, 14}. According to our reconstruction, high temperatures—similar to those observed in the twentieth century before 1990—occurred around ad 1000 to 1100, and minimum temperatures that are about 0.7 K below the average of 1961–90 occurred around ad 1600. This large natural variability in the past suggests an important role of natural multicentennial variability that is likely to continue.

1. Department of Meteorology, Stockholm University, SE-106 91 Stockholm, Sweden
2. Dynamical-Stochastical Laboratory, Hydrometeorological Research Centre of Russia, Bolshoy Predtechensky Lane 11/13, Moscow 123 242, Russia
3. Department of Physical Geography and Quaternary Geology, Stockholm University, SE-106 91 Stockholm, Sweden

Correspondence to: Anders Moberg¹ Correspondence and requests for materials should be addressed to A.M. (Email: anders.moberg@misu.su.se).

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