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Multiproxy summer and winter surface air temperature field reconstructions for southern South America covering the past centuries |
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| Authors: | R Neukom J Luterbacher R Villalba M K??ttel D Frank P D Jones M Grosjean H Wanner J-C Aravena D E Black D A Christie R D??Arrigo A Lara M Morales C Soliz-Gamboa A Srur R Urrutia L von Gunten |
| Institution: | 1. Oeschger Centre for Climate Change Research (OCCR), University of Bern, Bern, Switzerland 2. Institute of Geography, Climatology and Meteorology, University of Bern, Bern, Switzerland 3. Department of Geography; Climatology, Climate Dynamics and Climate Change, Justus Liebig University of Giessen, Giessen, Germany 4. Instituto Argentino de Nivolog??a, Glaciolog??a y Ciencias Ambientales (IANIGLA), CONICET, Mendoza, Argentina 5. Department of Earth and Space Sciences, University of Washington, Seattle, USA 6. Swiss Federal Research Institute WSL, 8903, Birmensdorf, Switzerland 7. Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK 8. Centro de Estudios Cuaternarios de Fuego Patagonia y Ant??rtica (CEQUA), Avenida Bulnes 01890, Punta Arenas, Chile 9. School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, USA 10. Laboratorio de Dendrocronolog??a, Facultad de Ciencias Forestales y Recursos Naturales, Universidad Austral de Chile Valdivia, Casilla 567, Valdivia, Chile 11. Tree-Ring Laboratory, Lamont-Doherty Earth Observatory, Earth Institute at Columbia University, Palisades, NY, USA 12. N??cleo Cient??fico Milenio FORECOS, Fundaci??n FORECOS, Valdivia, Chile 13. Section of Ecology and Biodiversity, Faculty of Science, Institute of Environmental Biology, Utrecht University, P.O. Box 80084, 3508 TB, Utrecht, The Netherlands 14. Department of Geosciences, Climate System Research Center, University of Massachusetts, Amherst, USA |
| Abstract: | We statistically reconstruct austral summer (winter) surface air temperature fields back to ad 900 (1706) using 22 (20) annually resolved predictors from natural and human archives from southern South America (SSA). This represents the first regional-scale climate field reconstruction for parts of the Southern Hemisphere at this high temporal resolution. We apply three different reconstruction techniques: multivariate principal component regression, composite plus scaling, and regularized expectation maximization. There is generally good agreement between the results of the three methods on interannual and decadal timescales. The field reconstructions allow us to describe differences and similarities in the temperature evolution of different sub-regions of SSA. The reconstructed SSA mean summer temperatures between 900 and 1350 are mostly above the 1901?C1995 climatology. After 1350, we reconstruct a sharp transition to colder conditions, which last until approximately 1700. The summers in the eighteenth century are relatively warm with a subsequent cold relapse peaking around 1850. In the twentieth century, summer temperatures reach conditions similar to earlier warm periods. The winter temperatures in the eighteenth and nineteenth centuries were mostly below the twentieth century average. The uncertainties of our reconstructions are generally largest in the eastern lowlands of SSA, where the coverage with proxy data is poorest. Verifications with independent summer temperature proxies and instrumental measurements suggest that the interannual and multi-decadal variations of SSA temperatures are well captured by our reconstructions. This new dataset can be used for data/model comparison and data assimilation as well as for detection and attribution studies at sub-continental scales. |
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