Figure 1.
Tree ring based reconstructions of ENH temperatures.
The series have been scaled to mean annual land (20-90°N)
extratropical temperatures over the 1850-1988 period.
DWJ2006: D'Arrigo et al. 2006; ECS2002: Esper et al. 2002;
BRF2000: Briffa 2000.
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A matter of divergence: Tracking recent warming at hemispheric scales
using tree ring data.
Journal of Geophysical Research - Atmospheres
Vol. 112, D17103, doi:10.1029/2006JD008318
11 September 2007.
Rob Wilson1,2, Rosanne D'Arrigo2,
B. Buckley2, U. Büntgen3, J. Esper3,
D. Frank3, B. Luckman4, S. Payette5,
R. Vose6, and D. Youngblut7
1 Grant Institute, University of Edinburgh, Edinburgh, UK
2 Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Palisades, New York, USA
3 Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
4 Department of Geography, University of Western Ontario, London, Ontario, Canada
5 Centre d'Études Nordiques, Université Laval, Québec, Quebec, Canada
6 National Climatic Data Center, Asheville, North Carolina, USA
7 Department of Geography and Environmental Studies, Carleton University,
Ottawa, Ontario, Canada
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ABSTRACT:
No current tree ring (TR) based reconstruction of extratropical Northern
Hemisphere (ENH) temperatures that extends into the 1990s captures the
full range of late 20th century warming observed in the instrumental
record. Over recent decades, a divergence between cooler reconstructed
and warmer instrumental large-scale temperatures is observed.
We hypothesize that this problem is partly related to the fact that
some of the constituent chronologies used for previous reconstructions
show divergence against local temperatures in the recent period.
In this study, we compiled TR data and published local/regional
reconstructions that show no divergence against local temperatures.
These data have not been included in other large-scale temperature
reconstructions. Utilizing this data set, we developed a new, completely
independent reconstruction of ENH annual temperatures (1750-2000).
This record is not meant to replace existing reconstructions but
allows some degree of independent validation of these earlier studies
as well as demonstrating that TR data can better model recent warming
at large scales when careful selection of constituent chronologies is
made at the local scale. Although the new series tracks the increase in
ENH annual temperatures over the last few decades better than any
existing reconstruction, it still slightly under predicts values in
the post-1988 period. We finally discuss possible reasons why it is
so difficult to model post-mid-1980s warming, provide some possible
alternative approaches with regards to the instrumental target and
detail several recommendations that should be followed in future
large-scale reconstruction attempts that may result in more robust
temperature estimates.
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