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Revisiting the lower stratospheric water vapour trend from the 1950s to 1970s

Previous work showed a near‐continuous increase in stratospheric water vapour between the 1950s and 1990s from a variety of instruments, without recourse to fits between instruments. We reassess the trend from the earliest, the UK frost‐point hygrometer, 1954–1976. An error in previous work omitted to transform values from ppmm to ppmv. When corrected, they fit more convincingly with measurements by later frost‐point hygrometers. Minor instrument changes between the 1950s and 1970s do not introduce a potential bias to the trend but do increase its error. If the full 1970s data are included, the trend becomes 2.1 ± 0.8%/year (two‐sigma). Copyright © 2011 Royal Meteorological Society