New paper shows Greenland was warmer during the 1930's and 1400's than the present

A new paper published in Climate of the Past reconstructs Greenland temperatures over the past 800 years and shows that reconstructed temperatures were higher in the 1930's and 1400's than at the end of the record in the year 2000. The paper also finds Greenland temperatures correlated to "solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO)." The Medieval Warming Period 1000 years ago is not included in this 800 year reconstruction, but Greenland ice cores demonstrate that the Medieval, Roman, Minoan, Egyptian, and other unnamed warming periods were all warmer than modern Greenland temperatures.

Reconstructed Greenland temperatures shown in blue bottom graph were higher in the 1930's and 1400's than at the end of the record in the year 2000. Michael Mann's bogus hockey stick is shown  for comparison in green in top graph. 

Clim. Past, 9, 583-596, 2013
www.clim-past.net/9/583/2013/
doi:10.5194/cp-9-583-2013
On the origin of multidecadal to centennial Greenland temperature anomalies over the past 800 yr

T. Kobashi^1,2, D. T. Shindell³, K. Kodera^4,5, J. E. Box^6,7, T. Nakaegawa⁴, and K. Kawamura^1
1National Institute of Polar Research, 10-3 Midoricho, Tachikawa, Tokyo, 190-8518, Japan
²Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA
³NASA Goddard Institute for Space Studies, New York, NY 10025, USA
⁴Meteorological Research Institute, Tsukuba, 305-0052, Japan
⁵Solar Terrestrial Environment Laboratory, Nagoya University, Nagoya, Japan
⁶Byrd Polar Research Center, The Ohio State University, Columbus, OH 43210, USA
⁷Department of Geography, The Ohio State University, Columbus, OH 43210, USA
 Abstract. The surface temperature of the Greenland ice sheet is among the most important climate variables for assessing how climate change may impact human societies due to its association with sea level rise. However, the causes of multidecadal-to-centennial temperature changes in Greenland temperatures are not well understood, largely owing to short observational records. To examine these, we calculated the Greenland temperature anomalies (GTA_[G-NH]) over the past 800 yr by subtracting the standardized northern hemispheric (NH) temperature from the standardized Greenland temperature. This decomposes the Greenland temperature variation into background climate (NH); polar amplification; and regional variability (GTA_[G-NH]). The central Greenland polar amplification factor as expressed by the variance ratio Greenland/NH is 2.6 over the past 161 yr, and 3.3–4.2 over the past 800 yr. The GTA_[G-NH] explains 31–35% of the variation of Greenland temperature in the multidecadal-to-centennial time scale over the past 800 yr. We found that the GTA_[G-NH] has been influenced by solar-induced changes in atmospheric circulation patterns such as those produced by the North Atlantic Oscillation/Arctic Oscillation (NAO/AO). Climate modeling and proxy temperature records indicate that the anomaly is also likely linked to solar-paced changes in the Atlantic meridional overturning circulation (AMOC) and associated changes in northward oceanic heat transport.

 Final Revised Paper (PDF, 7995 KB)   Discussion Paper (CPD)   Special Issue