Northern Hemisphere Annual Temperatures from Low- and High-Resolution Proxy Data over the last 2000 Years

A. Moberg, D.M. Sonechkin, K. Holmgren, N.M. Datsenko, and W. Karlén Complete Scientific Reference The reconstruction from Moberg et al. (2005) utilizes complementary information from proxy data that preserve both low- and high-frequency climate information. High-resolution data from tree rings reflect annual to multidecadal variability best and are precisely dated to the calendar year. The low resolution proxy records used here, from ice cores, boreholes, cave stalagmites, and lake and ocean sediments, contain information at centennial scales, but are based on less precise dating. A methodology based on wavelet transformation was used to isolate the climate information at the appropriate frequencies for each of the two types of data. The resulting reconstruction combines this information to include climate variability at annual to centennial scale frequencies. The reconstruction of Northern Hemisphere annual temperature anomalies is scaled to the 1961-1990 instrumental mean temperature, in degrees K (equivalent to degrees C). The Northern Hemisphere mean annual temperature from instrumental records has been added to this graph (in red) for comparison and is scaled to the same mean period. The Moberg reconstruction shares the larger degree of multicentennial variability with the borehole reconstructions (see Huang 2005), but the pattern of variability is very similar to that of the high-resolution reconstructions. The authors suggest that the greater multicentennial variability could be due to natural (solar and volcanic) forcing larger than previously thought. However, model experiments indicate that the recent warming is unlikely to be due to natural forcing alone. As with the other reconstructions, regardless of the proxy data used, this reconstruction indicates that the temperatures of the last two decades are warmer than any other period in the past two millennia.

Northern Hemisphere instrumental temperature series (in red) from: Smith, T.S., R.W. Reynolds, 2005. A Global Merged Land.Air.Sea Surface Temperature Reconstruction Based on Historical Observations (1880.1997). Journal of Climate, 18, 2012-2036.

Moberg et al. 2005 data and information

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