An ice-core record of atmospheric response to anthropogenic sulphate and nitrate

RECORDS of sulphate and nitrate concentrations in ice cores show that these concentrations have increased recently because of the long-range transport of pollution from middle latitudes1–5. But these records have been neither complete enough nor long enough to allow an assessment of their sensitivity to variations in the emissions of sulphate and nitrate precursors. We have now analysed sections from an ice core in South Greenland which have allowed us to extend its sulphate and nitrate record back from 1869 to 1767. This longer record has enabled us to determine the pre-industrial natural interannual variability of non-sea-salt sulphate and nitrate. We find that the background concentration in the remote atmosphere over South Greenland is sensitive to changes in the anthropogenic emissions of sulphate and nitrate, and responds to these variations on a timescale of the order of decades