Recent severe heat waves in central Europe: how to view them in a long-term prospect?

摘要

The study examines whether recent occurrences of severe heat waves in central Europe were exceptional in the context of past fluctuations, and estimates their recurrence probabilities under several climate change scenarios. Using data from a network of meteorological stations in the Czech Republic since 1961, it is found that 1994 was the year with the most severe heat waves over majority of the area. The other seasons with enhanced heat wave characteristics were 1992, 2003 and 2006. Analysis of the long-term temperature series at Prague-Klementinum reveals that the July 2006 heat wave, covering 33 consecutive days, was the longest and most severe individual heat wave since 1775. Probabilities of long and severe heat waves are estimated from daily temperature series generated by a first-order autoregressive model with a deterministic component (incorporating a seasonal cycle and a long-term trend). The model is validated with respect to the simulation of heat waves in present climate (1961–2006) and subsequently run under several assumptions reflecting various rates of summer warming over 2007–2100. The return period of a heat wave reaching or exceeding the length of the 2006 heat wave in Prague is estimated to be around 120 years in 2006. Owing to an increase in mean summer temperatures, probabilities of very long heat waves have already risen by an order of magnitude over the recent 25 years, and are likely to increase by another order of magnitude by around 2040 under the summer warming rate assumed by the mid-scenario. Even the lower bound scenario yields a considerable decline of return periods associated with intense heat waves. Nevertheless, the most severe recent heat waves appear to be typical rather of a late 21st century than a mid-21st century climate.