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Trends and oscillations in the Indian summer monsoon rainfall over the last two millennia.

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posted on 22.01.2016, 00:00 authored by A. Sinha, G. Kathayat, H. Cheng, S.F.M. Breitenbach, M. Berkelhammer, M. Mudelsee, J. Biswas, R.L. Edwards
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 anthropogenicforced changes in monsoon rainfall will remain difficult to detect against a backdrop of large natural variability.

Funding

We gratefully acknowledge the Chinese National Science Foundation grants to H.C. (NBRP 2013CB955902 and NSFC 41230524) and the National Science Foundation grants to A.S. (ATM: 0823554), R.L.E. and H.C. (1211299, 1103403 and 1337693) for funding this research. S.F.M.B. acknowledges financial support from the Swiss National Foundation (Sinergia grant CRSI22-132646/1).

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Publisher Statement

This is the copy of an article published in Nature Communications © 2015 Nature Communications. 2015. 6. DOI: 10.1038/ncomms7309. ©The Author(s).

Publisher

Nature Publishing Group

issn

2041-1723

Issue date

17/02/2015

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