Cloudbursts in Piedmont and Val d'Aosta:what role for global warming?

For climatologist Massimiliano Fazzini, even if we cannot really speak of "extreme events", overheating has certainly had an impact.

• Piedmont and Val d'Aosta were hit by floods in the middle of summer, while the French and Swiss Alpine slopes were also severely affected.
• According to the climatologist Massimiliano Fazzini, it is too early to talk about an extreme event and by chance two opposing air masses collided right in the mountains.
• However, the freezing point at 4,000 meters and the evident "thermal forcing" that has been underway for 50 years make the responsibility for global warming clear.

The Mediterranean summer is now well advanced but, while in the south and central Italy temperatures have soared above 40 degrees, Piedmont and Val d'Aosta (as well as, on the other side, the French and Swiss Alpine slopes) were hit by real floods which caused extensive damage due to landslides and landslides. Three victims were also recorded on the French side, in Switzerland two, in Italy none but Cogne remained completely isolated due to the closure of the only connecting road, a large part of the town was left without water, and the aqueduct was damaged.Huge disruption also occurred in Cervinia and in various areas of the province of Verbania, with damaged bridges and some isolated valleys.

Italy, as always, has already set in motion for Piedmont and Val d'Aosta:in a virtuous way, with emergency rescue intervention always ready (unlike what often happens with prevention);in a less virtuous way, splitting between those who speak of "exceptional meteorological events" and climate change, and those who instead dismiss everything as normal "bad weather", bringing an overall cool and rainy June to Italy as presumed proof of the absence of a change ( forgetting Copernicus data that continues to certify global records of temperatures month after month).

According to the climatologist Massimiliano Fazzini, Chair of the Climate Risk Team at Italian Society of Environmental Geology "we are once again faced with a dramatic outcome of intense meteorological phenomena, harbingers of damage and fear, but it is urgent to try to clarify the concepts, which are often used in a not entirely correct manner, in a context that needs of clarity."

Was it an exceptional event in Piedmont and Val d'Aosta?

Let's start first from the increasingly used concept of meteoric exceptionality:according to Fazzini, despite the meteorological phenomenon having affected a very large territory "from a first superficial analysis of the historical data, only at the rain gauge of Noasca – in Valle Orco, with 172 millimeters of rain fell, of which 127 in 3 hours – the cumulative daily, hourly and three-hourly rainfall can be defined as statistically exceptional”.

This it doesn't mean minimizing, on the contrary, simply admit to the lack of sufficiently extensive data from a temporal point of view:“Almost all the rain gauges analyzed have short-term historical series or detection inhomogeneities in the series itself, so stating that the precipitation at that precise point is exceptional is scientifically incorrect.Therefore it is only possible to state that the Noasca rain gauge can have return times that go back over centuries".Translated into simple words, the fact that it was not an exceptional event is even worse:it means that we can expect events of this type also in the coming years, apart from Noasca.

Was it a “simple” meteorological event?

According to the climatologist Fazzini, the floods that hit the Alps were also caused by an unfortunate chain of events: not exceptional but almost, and independent of climate change.“The nature of the precipitation was generated by a decidedly complex and rather rare situation:an intense convergence in the area affected by the atmospheric events between very humid and unstable air within the polar jet and an advection of very humid and warm currents coming from the south-eastern Mediterranean".Two opposing and contrary currents that collided precisely in an area "with a very complex orography, with peaks that are among the highest on the European continent, which has favored intense upward movements".

Was it global warming's fault?

Certainly a serious anomaly that facilitated what happened was that, at least in the early afternoon of last Saturday, the freezing point was close to 4 thousand metres, (a very high share, but not a record) and therefore intense rainfall occurred rain up to 3,400-3,600 meters above sea level, in areas where it usually snows rather than rain, causing the water to flow down the valley much more slowly than what happened this time.Even in this case, however, how much it rained at altitude "no one knows, given that we do not have any quantitative monitoring tools available at altitudes above 2300 meters above sea level other than the very approximate estimate of the precipitation at the Plateau Rosa glacier, at the head of the Marmore Torrent”.

Certainly, explains Fazzini, "the precipitation occurred in liquid form up to above 3,500 metres, affecting almost all of the mountain basins and falling on saturated soil due to previous rains and the melting of the snow which was still very abundant at high altitudes.Violent torrential floods and extensive debris flows, often recurring, have caused extensive and widespread impacts in the valleys of the Orco, Soana and Stura di Lanzo streams and of the five minor watersheds that characterize the Cogne Valley, with a magnitude even higher than some events that occurred in the area, in the summers of the 90s, between 1994 and 1996".If the freezing temperatures at very high altitudes, which is a symptom of the rise in global temperatures, is the original cause of the flooding of the valleys, then yes:at least in part we can also blame climate change.

But above all, are we in danger?

According to Fazzini, to date the most scientifically correct answer to the question of whether climate change has anything to do with it or not "is no”.Certainly not out of denial, but only because we do not yet have sufficient statistical data to support it, for the reasons we have seen above.“On the one hand, the thermal forcing active for more than half a century on the entire planet determines an ever-increasing quantity of energy available to the complex and chaotic sea-atmosphere system;it is therefore logical to expect increasingly extreme and temporally frequent atmospheric phenomena".

On the other hand, continues Fazzini, "if statistics confirmed that every intense event - be it meteoric, thermal or hydrological - corresponds to a new record or at least one of the highest numbers in a historical series of data, then there would no longer be any doubt:scientifically we would already be in a new climate, with more risks for the population.The human being, who has certainly and in various ways caused this imbalance in atmospheric thermodynamics and beyond, now he must try to adapt to these new critical situations, trying, once and for all and with as much common sense as possible, to mitigate this risk that is increasingly present in everyday life.And we believe there is very little time left."The subtext is clear:to make the best use of it we must rely on science.