ICTP Climate Research in Nature Geoscience

Global warming may not make future summers in the European Alps as dry as global climate models have predicted, but could increase the occurrence of extreme rain events and thus the risk of floods. According to new research led by the Abdus Salam International Centre for Theoretical Physics (ICTP), summer rain at high Alpine elevations, and particularly intense convection, could actually increase, thanks in part to the complex terrain of the region.

The wetter weather predictions are the result of simulations performed by ICTP climate researchers using the Centre’s internationally renown regional climate model RegCM4, as well as other European modeling groups, and may change the current view of how global warming will affect water resources of the Alpine region.

As many a hiker will know, the European Alps have a complex landscape of peaks and slopes. Climate modellers have long hypothesized that topography such as this could affect local weather patterns, but these local-scale details are lost in the broader resolutions covered by global climate models. However, at a scale of about 12 kilometers, regional climate models, including ICTP's RegCM, can produce high-resolution climate simulations. With such models, researchers were able to zoom in to local phenomena that might affect weather patterns, such as the Alpine terrain, to paint a more detailed picture of the local climate. While nearly all global climate models predict dryer summers over the Alps in the future, the ICTP researchers found that the European Alps’ complex topography could indeed cause an increase in rainfall at high elevations. This is because an enhanced summer warming at higher elevations, along with greater moisture, combine to create greater convective rainfalls. While on the one hand this implies increased summer water availability over the region, it also increases the risk of extreme destructive events. The team of researchers also found that the model projections are consistent with trends observed in recent decades over the Alpine precipitation.

Results of the research have been published in the science journal Nature Geoscience (doi: 10.1038/NGEO2761); the paper is titled 'Enhanced summer convective rainfall at Alpine
high elevations in response to climate warming'.

Lead author Filippo Giorgi, who heads ICTP’s Earth System Physics section, says that the results validate the importance of regional climate models such as RegCM. “Our findings show that the high resolution simulations performed by regional climate models can provide valuable refined information on climate change scenarios,” he explains. In particular, Giorgi points out, the ability of the high-resolution models to simulate topographic feedbacks is especially valuable for the modeling community. “It would be interesting to see whether our conclusions, which challenge the picture obtained by global models, could be applied to other mountainous areas of the world,” he says.

The ICTP RegCM model is flexible, portable and easy to use by climate researchers. It can be applied to any region of the world, with grid spacing of up to about 10 km, and can be used for a wide range of studies, from process studies to paleoclimate and future climate simulations. It is currently used by a large scientific community, including in particular scientists from developing countries.