Figure 3.
Composite NH temperature reconstructions & published NH reconstructions.
Click for larger version.
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Proxy-based reconstructions of hemispheric
and global surface temperature variations
over the past two millennia
Proceedings of the National Academy of Sciences
Vol. 105, No. 36, pp. 13252-13257, September 9, 2008.
doi:10.1073/pnas.0805721105
Michael E. Mann1, Zhihua Zhang1, Malcolm K. Hughes2,
Raymond S. Bradley3, Sonya K. Miller1, Scott Rutherford4,
and Fenbiao Ni 2.
1 Department of Meteorology and Earth and Environmental Systems Institute,
Pennsylvania State University, University Park, PA 16802
2 Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721
3 Department of Geosciences, University of Massachusetts, Amherst, MA 01003-9298
4 Department of Environmental Science, Roger Williams University, Bristol, RI 02809
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ABSTRACT:
Following the suggestions of a recent National Research Council report
[NRC (National Research Council) (2006) Surface Temperature Reconstructions
for the Last 2,000 Years (Natl Acad Press, Washington, DC).], we reconstruct
surface temperature at hemispheric and global scale for much of the last
2,000 years using a greatly expanded set of proxy data for decadal-to-centennial
climate changes, recently updated instrumental data, and complementary methods
that have been thoroughly tested and validated with model simulation experiments.
Our results extend previous conclusions that recent Northern Hemisphere surface
temperature increases are likely anomalous in a long-term context. Recent warmth
appears anomalous for at least the past 1,300 years whether or not tree-ring
data are used. If tree-ring data are used, the conclusion can be extended to
at least the past 1,700 years, but with additional strong caveats.
The reconstructed amplitude of change over past centuries is greater than
hitherto reported, with somewhat greater Medieval warmth in the Northern Hemisphere,
albeit still not reaching recent levels.
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