Trends and oscillations.pdf (1005.43 kB)
Trends and oscillations in the Indian summer monsoon rainfall over the last two millennia.
journal contribution
posted on 2016-01-22, 00:00 authored by A. Sinha, G. Kathayat, H. Cheng, S.F.M. Breitenbach, M. Berkelhammer, M. Mudelsee, J. Biswas, R.L. EdwardsObservations 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.