Climate change in Ireland from precipitation and stream ̄ow observations

On the basis of General Circulation Model (GCM) experiments with increased CO2, many parts of the northern latitudes including western Europe, are expected to have enhanced hydrologic cycles. Using observations of precipitation and stream ̄ow from Ireland, we test for climatic and hydrologic change in this maritime climate of the northeast Atlantic. Five decades of hourly precipitation (at eight sites) and daily stream ̄ow at four rivers in Ireland were investigated for patterns of climate variability. An increase in annual precipitation was found to occur after 1975. This increase in precipitation is most noticeable on the West of the island. Precipitation increases are signi®cant in March and October and are associated with increases in the frequency of wet hours with no change in the hourly intensities. Analysis of stream ̄ow data shows the same trends. Furthermore, analysis of extreme rainfall events show that a much greater proportion of extremes have occurred in the period since 1975. A change also occurred in the North Atlantic Oscillation (NAO) index around 1975. The increased NAO since 1975 is associated with increased westerly air ̄ow circulation in the Northeast Atlantic and is correlated with the wetter climate in Ireland. These climatic changes have implications for water resources management particularly ̄ood analysis and protection. Ó 1999 Elsevier Science Ltd. All rights reserved.