Climate: Extreme weather events on the rise in Italy by 2100

An ENEA study ^[1] shows that by the end of the century Italy and the entire Mediterranean basin are projected to face a general increase in temperatures and an average reduction in precipitation. The study ^[2] also highlights that these changes will be accompanied by a marked increase in the frequency of extreme events, with intense thunderstorms and flash floods, particularly during the autumn season in the Alpine regions.

“We used ultra–high-resolution regional climate projections (down to 5 km), which—like a magnifying glass—allowed us to assess with exceptional precision the impacts expected by 2100, particularly with regard to extreme events and local phenomena,” explained Maria Vittoria Struglia, coordinator of the study and researcher at the ENEA Climate Models and Services Laboratory. “Regional climate projections,” she said, “are an extremely valuable tool for more reliably estimating the impacts of climate change at the local scale. They also make it possible to design targeted adaptation strategies that take territorial and seasonal specificities into account.”

The ENEA team carried out simulations for both the past climate (1980–2014), useful for quantifying changes already under way, and the future climate (2015–2100), using three reference socioeconomic and climate scenarios. ^[3].

The ENEA team carried out simulations for both the past climate (1980–2014), useful for quantifying changes already under way, and the future climate (2015–2100), using three reference socioeconomic and climate scenarios. These scenarios range from those in which environmental sustainability policies are implemented to those in which decarbonization policies are not central to development models. On the basis of these projections, the effects of climate change on surface temperature and precipitation in Italy were estimated.

According to the study, mountain areas are expected to experience an increase in summer temperatures, with peaks of up to +4.5 °C, and up to +3.5 °C in autumn under the highest-impact scenario (Fig. 1). This represents a significant warming that, in these regions, is missed by low-resolution global climate models.

As for precipitation, projections indicate overall drier conditions, particularly during summer (Fig. 2). However, under the two most critical scenarios, an increase in both the frequency and intensity of extreme weather events is expected, especially in northern Italy, particularly in the Alpine and sub-Alpine areas (Fig. 3).

“A more detailed examination of  the ENEA study shows that by the end of the century (2071–2100) an increase in the intensity of winter precipitation may occur, especially in the Western Alps, in contrast to the Eastern Alps, where a slight decrease is observed. In southern Italy, precipitation intensity is expected to decline, with a significant decline over the main mountain ranges of Sicily (Fig. 4).

In spring, the pattern is similar to winter, but with a more widespread increase in intensity across the entire Alpine arc. During summer, a generalized decrease in the intensity of extreme summer precipitation is observed, especially along the Tyrrhenian coasts. In autumn, under the most severe scenario, a significant increase in the intensity of extreme rainfall is recorded over much of Italy, with larger increases in areas already experiencing severe climate impacts (Northern Italy).

“High-resolution regional simulation show changes in precipitation that differ from—and in some areas are opposite to—those of low-resolution global models.”

“In recent years, the development of increasingly powerful technologies has enabled much more detailed regional climate projections[3] allowing to assess the local impacts of climate change and climate-related risks and to support adaptation and mitigation policies. This represents significant progress for the Mediterranean region, a climate hotspot characterized by a highly heterogeneous morphology (a semi-enclosed basin surrounded by high and complex mountainous reliefs), which requires high-resolution analyses. The region is in fact particularly vulnerable to the impacts of extreme weather events at a local scale, which can significantly affect the well-being and economy of local communities” concluded, Struglia.

[1] This study was carried out as part of the following projects: KNOWING, funded by the European Union under the Horizon Europe research and innovation program; RETURN, funded by the European Union under the Next Generation EU program – National Recovery and Resilience Plan (PNRR), Mission 4, Component 2, Investment 1.3;  (D.D. 1243 of 08/02/2022, PE0000005); ICSC National Research Center on High Performance Computing, Big Data and Quantum Computing, funded by the European Union under the Next Generation EU program – National Recovery and Resilience Plan (PNRR), Mission 4, Component 2, Investment 1.4.

[2] SSP1-2.6, SSP2-4.5 and SSP5-8.5.

[3] Called Convection Permitting Models (CPM), they operate at a spatial resolution of the order of 1–4 km, sufficient to explicitly simulate atmospheric convection, i.e. the vertical motions that give rise to clouds and intense precipitation. ​Unlike lower-resolution models, which must simplify these phenomena through parameterizations, CPMs are able to reproduce them directly, improving their accuracy.