Flaws are revealed in a highly cited database that dates back more than two centuries.
Scientists have identified biased data in an iconic meteorological record, and are now challenging conclusions about long-term precipitation trends in England, Wales and possibly other regions.
The England and Wales Precipitation (EWP) series is a continuous monthly record of British snow and rainfall, stretching back to 1766. For decades, climate scientists have used this record — one of the longest-running available — to examine precipitation and atmospheric-circulation patterns in northwest Europe.
Conor Murphy at Maynooth University, Ireland, and his colleagues drew on independent data, including long-term measurements of British snowfall, to reconstruct the record’s early portion. Their reconstruction showed that the EWP underestimated winter precipitation before 1870, whereas summer rainfall was overestimated before 1820. As a result, the widely accepted conclusion that winters have become wetter and summers dryer since 1766 appears to be an artefact.