[Vision2020] National Center for Atmospheric Research: Arctic Warming Overtakes 2, 000 Years of Natural Cooling

[Ted Moffett]

 http://www.ucar.edu/news/releases/2009/arctic2k.jsp Arctic Warming
Overtakes 2,000 Years of Natural Cooling

September 03, 2009

BOULDER—Arctic temperatures in the 1990s reached their warmest level of any
decade in at least 2,000 years, new research indicates. The study, which
incorporates geologic records and computer simulations, provides new
evidence that the Arctic would be cooling if not for greenhouse gas
emissions that are overpowering natural climate patterns.

The international study, led by Northern Arizona University and the National
Center for Atmospheric Research (NCAR), will be published in the September 4
edition of Science. It was primarily funded by the National Science
Foundation, NCAR's sponsor.

The scientists reconstructed summer temperatures across the Arctic over the
last 2,000 years by decade, extending a view of climate far beyond the 400
years of Arctic-wide records previously available at that level of detail.
They found that thousands of years of gradual Arctic cooling, related to
natural changes in Earth's orbit, would continue today if not for emissions
of carbon dioxide and other greenhouse gases.
-------------------------
http://www.sciencemag.org/cgi/content/abstract/325/5945/1236

*Science* 4 September 2009:
Vol. 325. no. 5945, pp. 1236 - 1239
DOI: 10.1126/science.1173983
 Reports Recent Warming Reverses Long-Term Arctic Cooling*Darrell S.
Kaufman,1,* David P. Schneider,2 Nicholas P. McKay,3 Caspar M.
Ammann,2Raymond S. Bradley,
4 Keith R. Briffa,5 Gifford H. Miller,6 Bette L. Otto-Bliesner,2 Jonathan T.
Overpeck,3 Bo M. Vinther,7 Arctic Lakes 2k Project Members[image: {dagger}]
*

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 2000 years,
which indicates that a pervasive cooling in progress 2000 years ago
continued through the Middle Ages and into the Little Ice Age. A 2000-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 2000-year-long reconstruction occurring between 1950 and
2000.
-----------------------------------
Vision2020 Post: Ted Moffett
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.fsr.com/pipermail/vision2020/attachments/20090906/e4047b35/attachment.html