G&B Festival, Giulio Boccaletti: Drought increasingly intense due to the “thirst” of the atmosphere
MILAN. “The discussions on floods and droughts, on the engineering of territories to manage the new water cycle, have little to do with science or the environment: we need a political vision of the future and an economic plan to support it”. Giulio Boccaletti , scientific director of the Euro-Mediterranean Centre on Climate Change, calls himself an “anomalous scientist”. From the stage of the Green&Blue Festival , underway in Milan, he recalls how in the last century dams, canals, hydroelectric plants have transformed Italy from a poor country to the fifth industrial power. Then the weather statistics, on the basis of which those infrastructures had been designed, began to change. And the old works proved inadequate for the new reality.
One of the many confirmations of the “water” change came last Wednesday from a study published in Nature : global warming is making the atmosphere increasingly “thirsty”, which translates into increasingly severe droughts. The authors analyzed drought data from 1901 to 2022, finding a worsening trend. "Our results - the researchers write - suggest that atmospheric evaporative demand (AED) has increased drought severity by an average of 40% globally. Not only are typically arid regions becoming even drier, but humid areas are also experiencing drought trends. From 2018 to 2022, drought-affected areas increased by an average of 74% compared to the 1981-2017 period, with AED contributing 58% of this increase and playing an increasingly important role in causing droughts, and this trend is likely to continue".
"For at least ten years we have been diagnosing the warming of the planet in many different ways. This study reveals how complex the changes we are witnessing are,” comments Boccaletti. “Drought depends on how much water can stay on the ground, how much plants release through transpiration and how much the atmosphere is capable of absorbing. Aed is precisely the capacity of the air that flows over the surface to absorb water. Well, the characteristics of the atmosphere are changing: the average temperature, the wind speed, the turbulence. And this causes a greater absorption of water from the soil.”
But it is only one of the pieces of the complex change in the water cycle that for centuries had accustomed human societies to a relative regularity. “Then the temperature began to rise, the amount of water that the atmosphere absorbs began to change, the amount of ice began to decrease, snowfall began to drop even radically and the statistics of the past are no longer usable for planning infrastructures”, explains Boccaletti. Who adds: “The floods or waves of drought that we have seen in recent years are not just climate change. They are the failure of infrastructures that had been sized on the basis of different statistics. While climate change is gradual, we only notice the failure of the infrastructure when it occurs”.
And for the future? “We need a vision, to know where we want to go,” replies the scientist. “Let's take the reconstruction of Romagna after the flood. We should ask ourselves the question: how will we manage the water landscape that we are rebuilding? Do we want to rebuild Romagna to make it go back to how it was? But since it rains differently, it is hot differently, perhaps we should ask ourselves what we want Romagna to be like in 2050. At that point we would be able to answer questions like: how much water is needed? What to do with it? Do we put kiwis, corn or data centers? These choices determine the water resources and the works to be carried out.”
"Science – concludes Boccaletti – has a fundamental role in informing the public debate. But it has no normative value. And in any case the real crux of the debate remains: what countries do we want to build? In fifty years, what will our home be like? If you don't have an answer to these questions, science cannot enlighten you".
“From 2018 to 2022, the areas affected by water shortages increased by an average of 74 percent compared to the period 1981-2017.
La Repubblica
