Geophys. Res. Lett. 34, L07711 (2007)

Credit: PUNCHSTOCK

Checking Mediterranean rain gauges in winter may provide clues for predicting Europe's next deadly heat wave. Robert Vautard of France's Institut Pierre-Simon Laplace and colleagues have now discovered that a deficit of winter rainfall in southern Europe is a good indicator of high summertime temperatures and drought farther north.

Using meteorological data from over 100 sites in Europe, Vautard's team analysed the ten hottest European summers between 1948 and 2005, including 2003 when some 35,000 people died. All were preceded by southern European winters of below average rainfall. The water reservoir in Mediterranean soils plays a crucial role in maintaining this link, the researchers say.

During dry southern winters, soils release little moisture to the atmosphere. As a result, southerly winds blow warm dry air northward, reducing cloud cover and warming the air. Northern soils also dry faster, causing further warming from below. Scientists expect southern Europe to become increasingly dry, triggering more frequent heat waves and drought, as a result of climate change. Authorities can better prepare for extreme summer heat by studying rainfall patterns in the Mediterranean each winter.