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Published online on June 1, 2006, 10.1073/pnas.0603118103
PNAS | June 13, 2006 | vol. 103 | no. 24 | 8937-8942


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PHYSICAL SCIENCES / GEOLOGY
Solar modulation of Little Ice Age climate in the tropical Andes

P. J. Polissar*,{dagger}, M. B. Abbott{ddagger}, A. P. Wolfe§, M. Bezada, V. Rull||, and R. S. Bradley*

*Department of Geosciences, Morrill Science Center, University of Massachusetts, Amherst, MA 01003; {ddagger}Geology and Planetary Science, University of Pittsburgh, Pittsburgh, PA 15260; §Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB, Canada T6G 2E3; Departamento de Ciencias de la Tierra, Universidad Pedagógica Experimental Libertador, Avenida Paez, El Paraíso, Caracas, Venezuela; and ||Departament de Biologia Animal, Vegetal, i Ecologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Barcelona, Spain

Communicated by H. E. Wright, University of Minnesota, Minneapolis, MN, April 17, 2006 (received for review June 20, 2005)

The underlying causes of late-Holocene climate variability in the tropics are incompletely understood. Here we report a 1,500-year reconstruction of climate history and glaciation in the Venezuelan Andes using lake sediments. Four glacial advances occurred between anno Domini (A.D.) 1250 and 1810, coincident with solar-activity minima. Temperature declines of –3.2 ± 1.4°C and precipitation increases of {approx}20% are required to produce the observed glacial responses. These results highlight the sensitivity of high-altitude tropical regions to relatively small changes in radiative forcing, implying even greater probable responses to future anthropogenic forcing.

climate forcing | glacier reconstruction | moisture balance | Venezuela

Author contributions: M.B.A., A.P.W., and R.S.B. designed research; P.J.P., M.B.A., A.P.W., M.B., and V.R. performed research; P.J.P., M.B.A., M.B., V.R., and R.S.B. analyzed data; and P.J.P., M.B.A., A.P.W., and V.R. wrote the paper.

Conflict of interest statement: No conflicts declared.

{dagger}To whom correspondence should be sent at the present address: Department of Geosciences, 411 Deike Building, Pennsylvania State University, University Park, PA 16802. E-mail: ppolissa{at}geosc.psu.edu

© 2006 by The National Academy of Sciences of the USA


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