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Area of Expertise:Climatology, modeling, dendrochronology
"How and why does climate vary on interannual to century time scales?." I view this as the central question of what I call "meso-climatology". This approach overlaps with but differs from "neo-climatology" in which models arise from consideration of first principles and large masses of directly observed instrumental data on the atmosphere, land surface, oceans and cryosphere. The difference arises primarily by virtue of decreasing data density with antiquity and an interannual to millennial perspective. It is less often recognized that meso-climatology also differs in important respects from "paleo-climatology", where changes in the boundary conditions of the climate system impose very large scale changes that that can be well captured at a small number of locations, such as the onset and retreat of the Pleistocene glaciations. As a result of the relatively small changes in climate that occurred over the Holocene, it is much less likely that uniform, global responses will be observed, and so it is necessary to build relatively dense networks of proxy climate records of annual or close to annual resolution.
I focus on building large scale (continental to global) networks of instrumental and ‘proxy' climate records with defined chronology, temporal resolution and climate signal. In support of this general aim I work to:
- establish new kinds of tree ring record (new species, new regions, new variables) that may be used, in combination with other records, to ‘thencast' the behavior of the climate system. Recently, I have cooperated with Dr. Ramzi Touchan in the establishment of a major new dendroclimatic network in the Near East, and with Dr. Matthew Salzer on the expansion, enhancement and updating of millennial and multimillennial chronologies of bristlecone pine and its congeners. I continue to work on hemispheric and global reconstructions.
- explore the use of cell dimensions as climate proxies, and of the separate signals of ring width and density. A model for the simulation of tree-ring chronology building and the detection of time-dependent biases is under development with Dr. Kurt Kipfmueller of the University of Minnesota and Drs David Meko and Fenbiao Ni. I have initiated the installation of a new system for wood densitometry (The first Rinntech Lignostation in North America), intended to replace our X-ray densitometry facility.
- use climate reconstructions or ‘thencasts' to raise questions about the behavior of the climate system. These questions not only apply to the nature of the 20th century in comparison to earlier periods, but also to the potential existence of multimillennial "regimes" at the scale of the Pacific Basin and perhaps on even larger scales.
- base this on improved understanding of the mechanisms controlling tree-ring variability, primarily in collaboration with Academician Eugene Vaganov of the Russian Academy of Sciences and Dr. Michael Evans.