A rare triple-whammy of cyclones drove the deadly flooding that devastated much of northern Italy this month. Scientists have stated that climate change does not seem to be the cause of the intense rainfall. A team of researchers used computer simulations and past observations to look for evidence of human-caused warming behind the drenching. The study was undertaken to answer the question of whether and to what extent climate change was an influence in the flooding in Emilia-Romagna, Italy.
Flooding in Italy
World Weather Attribution compared what happened to a computer-simulated world of no human-caused warming and did not find the fingerprints of fossil-fuel-induced climate change, unlike in many past studies. The climate experts cautioned that more time for study is needed because having three exceptionally heavy downpours in such a short timeframe is so rare. The study estimated there was a 1-in-200 probability that three cyclones would strike within a three-week period.
The study’s findings corroborated earlier research that found that with human-induced climate change, the number of low-pressure systems in the Mediterranean has decreased. This leads to a reduction in heavy rainfall, offsetting the expected increase in heavy rain from global warming. Researchers also found that of the 19 models used, none of them showed a significant likelihood or intensity of such an event to occur. This suggests that in contrast to most parts of the world, there is indeed no detectable increase in heavy rainfall in the Emilia-Romagna region in spring.
The last of the three May floods was the most devastating and claimed 15 lives. The extremely heavy and concentrated rainfall triggered some 300 landslides and caused nearly two dozen rivers to overflow. The floodwaters were so high that firefighter and coastguard helicopters were needed to rescue some residents who climbed onto rooftops of three-story buildings to avoid drowning.
Climate Change and Flooding
Still, the climate experts cautioned that more time for study is needed. The study’s co-author Davide Faranda, a researcher in climate physics at the Pierre-Simon Laplace Institute in France, said, “This is not the end of the story.” Faranda stated that “remember there was a drought before” the first storm pummeled the Emilia-Romagna region on May 2, and “this (drought) was due to climate change.” He was referring to two years of scant or no rainfall that left land so parched it could not absorb the first rainfall. Drought derived mainly from the lack of Alpine snowfall, which usually replenishes the Po River and other smaller waterways in Italy’s north.
Emilia-Romagna is one of Italy’s most productive regions for agriculture and manufacturing. Like elsewhere in the north, during the nation’s post-war economic boom, much of the region was rapidly urbanized, depriving the area of terrain needed for drainage and increasing the risk of flooding. All that “has exacerbated the impacts of the heavy rainfall. However, this was an extremely rare event, and most infrastructure cannot reasonably be built to withstand such low-frequency events,” the scientists said in their findings.
The study found no evidence of human-caused warming behind the drenching rains that led to the triple-whammy of cyclones that drove Italy’s deadly flooding. The study’s findings suggest that in contrast to most parts of the world, there is no detectable increase in heavy rainfall in the Emilia-Romagna region in spring. Although the area has a history of severe flooding, the heavy rainfall over the first 21 days of May 2023 is the wettest event of this type in the record.