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Future projections about extreme events with significant impacts on national electric system

rapporti - Deliverable

Future projections about extreme events with significant impacts on national electric system

On the basis of Euro-CORDEX models an analysis about likely changes of the extreme weather events has been carried out with particular attention for wet-snow phenomena because of their significant impacts on electric-energy system.

The intensification of extreme weather events (strong winds, thunderstorms and snowstorms) entails serious risks for human activities and infrastructures. The aim of this work is to assess the impacts of likely changes in extreme events for the Italian electro-energy system by comparing the current climate (REF=1971–2000) with medium-term (FUT1=2021–2050) and long-term (FUT2=2051-2080) scenarios.

These events have been investigated by using a subset of ETCCDI indexes (standard indicators from the World Meteorological Organization Expert Team on Climate Change Detection and Indices) plus an ad hoc index to characterize the wet-snow frequency (WSF). Such indexes have been computed on the basis of 14 EURO-CORDEX simulations at horizontal resolution of 0.11° (about 12 km) under the emission scenario RCP 8.5.

At first an analysis of the models’ performances has been done making reference to MESAN data. Then two models, giving an unreliable description of the current climate, have been discarded in computing the above mentioned indexes. The future scenarios have been evaluated by averaging only the results with statistically significant differences respect to the REF period values. Moreover, the robustness of the results have been investigated by considering the degree of agreement about changes among the model projections.

The results highlight an exacerbation of the hazards, projected to become more serious in the second part of the century than the first one: the heat waves occurrences will likely increase of about 20-30% in the next decades, and 40-50% after the middle of the century; droughts are expected to become more frequent over time, increasing of about 5% and 10-20% in FUT1 and FUT2 respectively; severe storms and floods are also projected to increase from 10% to 30% in their occurrences. Instead wet-snow events are expected to damp ranging from less than -5% to -10% over the century. Analogously cold waves are likely to reduce of about 10-20% and 30-40% in FUT1 and FUT2 scenarios.

A further study has been undertaken to better characterize the wet-snow events expected in medium term, as in these last years heavy wet snowfalls have been causing serious problems for the safety and operation of the Italian Electric System (for instance, think of the event occurred in the Abruzzo region on January 16-18, 2017). There is a good agreement among the models in highlighting a wet-snow load increasing of about 70- 100% over the Alps, especially in the Northern and Western mountain regions, whereas a decrease of about 20-40% is expected in the Po valley with a medium confidence. In the Central and Southern Italy the signal has been found weaker (wet-snow is expected to decrease of about 10-20%) with low confidence. Larger uncertainties characterize the Central and Northern Apennines where the signal is almost absent, therefore no information can be inferred for these areas.

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