Recent Warming Reverses Long-Term Arctic Cooling, Science, 325 (2009)

Science (4 September 2009), Vol. 325, No. 5945, pp. 1236-1239; doi: 10.1126/science.1173983

Recent Warming Reverses Long-Term Arctic Cooling

1. Darrell S. Kaufman¹,*, 
2. David P. Schneider², 
3. Nicholas P. McKay³, 
4. Caspar M. Ammann², 
5. Raymond S. Bradley⁴,
6. Keith R. Briffa⁵, 
7. Gifford H. Miller⁶, 
8. Bette L. Otto-Bliesner², 
9. Jonathan T. Overpeck³, 
10. Bo M. Vinther⁷, and 
11. Arctic Lakes 2k Project Members†

1. ¹School of Earth Sciences and Environmental Sustainability, Northern Arizona University, Flagstaff, AZ 86011, USA.
2. ²Climate and Global Dynamics Division, National Center for Atmospheric Research, Boulder, CO 80305, USA.
3. ³Department of Geosciences, University of Arizona, Tucson, AZ 85721, USA.
4. ⁴Department of Geosciences, University of Massachusetts, Amherst, MA 01003, USA.
5. ⁵Climatic Research Unit, University of East Anglia, Norwich NR4 7TJ, UK.
6. ⁶Institute of Arctic and Alpine Research, University of Colorado, Boulder, CO 80309, USA.
7. ⁷Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark.

Abstract

The temperature history of the first millennium C.E. is sparsely documented, especially in the Arctic. We present a synthesis of decadally resolved proxy temperature records from poleward of 60° N covering the past 2,000 years, which indicates that a pervasive cooling in progress 2,000 years ago continued through the Middle Ages and into the Little Ice Age. A 2,000-year transient climate simulation with the Community Climate System Model shows the same temperature sensitivity to changes in insolation as does our proxy reconstruction, supporting the inference that this long-term trend was caused by the steady orbitally driven reduction in summer insolation. The cooling trend was reversed during the 20th century, with four of the five warmest decades of our 2,000-year-long reconstruction occurring between 1950 and 2000.

Received for publication 24 March 2009. Accepted for publication 22 June 2009.

*Correspondence : darrell.kaufman@nau.edu

http://www.sciencemag.org/content/325/5945/1236.abstract