J. Clim. http://doi.org/rfr (2014)

Prolonged periods of extremely hot weather — heatwaves — can have a deleterious effect on human health. Climate model simulations suggest that the duration and frequency of such events could grow over the coming century.

Ngar-Cheung Lau and Mary Jo Nath, of the NOAA Geophysical Fluid Dynamics Laboratory, USA, examined the distribution and dynamics of heatwaves in Europe between 1979 and 2008, using a high-resolution atmospheric model and reanalysis data. They identified three key regions where heatwaves have occurred most often: western Russia, eastern Europe and western Europe. The heatwaves were accompanied by anomalous anticyclonic systems, indicative of the involvement of large-scale atmospheric waves in heatwave development. Additional simulations with the atmospheric model, assuming a total warming of 4.5 W m−2 over the twenty-first century, indicate that the duration of individual heatwaves in Europe could grow by a factor of 1.4 to 2, with the frequency increasing by a factor of 2.2 to 4.5, by the end of the century.

Simulations with a coupled general circulation model suggest that the number of heatwave days will rise monotonically over the twenty-first century.