title: Trends and oscillations in the Indian summer monsoon rainfall over the last two millennia.
abstract: Observations show that summer rainfall over large parts of South Asia has declined over the past five to six decades. It remains unclear, however, whether this trend is due to natural variability or increased anthropogenic aerosol loading over South Asia. Here we use stable oxygen isotopes in speleothems from northern India to reconstruct variations in Indian monsoon rainfall over the last two millennia. We find that within the long-term context of our record, the current drying trend is not outside the envelope of monsoon's oscillatory variability, albeit at the lower edge of this variance. Furthermore, the magnitude of multi-decadal oscillatory variability in monsoon rainfall inferred from our proxy record is comparable to model estimates of anthropogenic-forced trends of mean monsoon rainfall in the 21st century under various emission scenarios. Our results suggest that anthropogenic-forced changes in monsoon rainfall will remain difficult to detect against a backdrop of large natural variability.
authors: Department of Earth Sciences, California State University Dominguez Hills, Carson, California 90747, USA.
authors: Ashish
authors: A
authors: Sinha
authors: Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China.
authors: Gayatri
authors: G
authors: Kathayat
authors: 1] Institute of Global Environmental Change, Xi'an Jiaotong University, Xi'an 710049, China [2] Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors: Hai
authors: H
authors: Cheng
authors: 1] Department of Earth Sciences, Eidgenössische Technische Hochschule, CH-8092 Zürich, Switzerland [2] Institute for Geology, Mineralogy &Geophysics, Ruhr-Universität Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany.
authors: Sebastian F M
authors: SF
authors: Breitenbach
authors: Department of Earth and Environmental Sciences, University of Illinois, Chicago, Illinois 60607, USA.
authors: Max
authors: M
authors: Berkelhammer
authors: Alfred Wegener Institute for Polar and Marine Research, 27570 Bremerhaven, Germany.
authors: Manfred
authors: M
authors: Mudelsee
authors: National Cave Research and Protection Organization, Raipur, CG 492001, India.
authors: Jayant
authors: J
authors: Biswas
authors: Department of Earth Sciences, University of Minnesota, Minneapolis, Minnesota 55455, USA.
authors: R L
authors: RL
authors: Edwards