Torrid heat, Mercalli debunks fake news

18 July 2023

"The heatwaves of recent years and these days have only one reason: global warming. The signal is clear'. Climate cycles? 'Nonsense: there are some physical reasons why climate cycles occur, but right now the only reason for such a large increase in temperatures is the burning of oil, coal and gas'. Climatologist and populariser of science Luca Mercalli, explains to ilfattoquotidiano.it what is causing the scorching heat (even) these days and what it means in terms of global warming, also debunking some fake news about climate change. 'We are seeing things we have never seen before: the hottest summer in the history of Europe was, at least so far, that of 2022, with over 60,000 victims,' he adds, recalling the estimate of researchers from the Instituto de Salud Global in Barcelona, authors of a recent article published in Nature Medicine. That of 2022 was also a record for Italy, on a par, however, with that recorded in 2003. "But for other countries it was really a first. Just think that last year there were 40 degrees even in London,' Mercalli explains. And the summer of 2023, so far, does not bode well.
Can you explain what is happening this week?
"The torrid heat is due to a large African anticyclone, i.e. a hot area coming from the Sahara. The whole Mediterranean is under the influence of this African air bubble. It is hot in Spain, Morocco, Algeria, Greece and Italy, where it envelops the whole of northern Italy, more or less reaching the Alps. Here, it comes into contact with cooler air from northern Europe. And that is why temperatures have also risen in Milan, but less. Monday's figures are 43-44 degrees between Sicily, Sardinia, and much of the south, and gradually dropping to 38-39 degrees in the Po Valley'.
What should we expect for the coming weeks?
"This situation in the North will die down on Friday, 21 July, while in the Centre-South it will continue at least until 25 July. If we are talking about the hottest summers in Europe, we cannot yet say whether we will break the 2022 record, because we do not have the overall data for the entire season, although the ingredients are all there'.
There are, however, other data concerning the entire planet.
"From 3 to 10 July 2023, the hottest week on Earth was recorded. We are talking, it must be emphasised, about the entire planet: air, atmosphere and oceans measured with all the instruments available in the world, from weather stations to buoys. And this is the most important data, because it tells us that the whole planet is warming up and, of course, locally there are these heat waves that today are with us and tomorrow are somewhere else. Right now, for example, we have California and China. The latter recorded 50 degrees, a temperature that should also be reached in California these days.
On global warming, a series of beliefs and fake news risk blurring the issue and slowing down the battle to tackle the climate crisis. All it takes is the perception of a cooler June, as was the case in Italy, to confuse ideas about the path the planet is on...
"Our perceptions are not like those of thermometers, they are mediated by many other psychological aspects. In fact, we perceived June as cool because it was very cloudy and it rained a lot, but in reality it was the 11th hottest in two hundred years. The fact is that if 30 degrees are recorded every day in a month, it is perceived as normal, average, whereas if 50 degrees are recorded in the same month on one day, that is the trace that remains. The judgement on hot summers, however, is made by thermometers and not by people's perception'.
Neither should the snowfall in Johannesburg, after eleven years, be confusing.
"It happened in South Africa, where it is winter because we are talking about the Southern Hemisphere. Last week, two centimetres of snow fell: a snowfall that occurs more or less every ten years. But it is not that a small local phenomenon, moreover in an austral winter, is at odds with global warming.
Yet heavy rainfall and floods are often fertile ground for climate denialism.
"A distinction must be made between extreme heat and floods. The latter have different causes. When we talk about heat waves, however, the signal is unambiguous: it is due to global warming. Heat also has an effect on rainfall, causing it to increase in some circumstances and decrease in others. So, to be clear, it is not that the flood in Emilia Romagna is the fault of global warming, but the flood was intensified by global warming and the effects of what happened are also the result of cementing and bad land use. Climatic floods have always existed, just think of the one in Florence in '66 and the one in Sarno. But climate change plays a small part in making the situation worse. Instead, this heat is new, unprecedented'.
What do you mean by 'unprecedented'?
"That these temperatures and this frequency of heatwaves are unparalleled in the last two hundred years, which is as long as we have data. But, from a number of surveys, such as those on glaciers, we know that they weren't there before either. And these surveys tell us that the last few years are the hottest ever. The week beginning on 3 July was the hottest in at least the last two centuries, considering that data from meteorological satellites have been available since 1979, they have been compared with those of previous observatories. This is important data, which should give us pause for thought'.
Yet, even in the face of scorching heat and records, we hear the catchphrase 'there is no warming, these phenomena occur with a certain cyclicity'. But is this really the case?"This is nonsense. It's not about cycles. Climatologists do just that, they try to understand why seasons or temperatures change. Cycles exist in the climate, but they must have a reason, which may be in the sun, in the position of the earth's orbit around the sun, or sometimes in ocean cycle currents. There are certain physical reasons why climate cycles occur. Here, right now these reasons are not operating, while what is operating is a human-induced forcing, namely the burning of oil, coal and gas. And this is not a natural cycle, because natural causes are not operating at this moment: the Sun is quiet, it is not that it is getting hotter because the Sun has become more violent, the Earth's axis is stable, the Earth's orbit we know how it behaves, and it will take 50,000 years for an ice age to arrive. So, right now, the heat is a result of mankind's CO2 emissions, which we have known for a hundred years'.
Again, the question from before, but with a long-term horizon. What should we expect in the coming years or decades?
"Simple. The temperature will continue to rise. Heat waves will become more frequent and more intense. It means that if we reach 45 degrees now, in a few years it will reach 50 degrees. The hottest temperature in the history of Italy's climate is the 48.8 degrees in Syracuse recorded on 11 August 2021, an Italian and European thermal record. If we exceeded that temperature these days, we would even have a new absolute record. However, slowly these numbers will get higher and higher, and there will be more and more days of extreme heat. In practice, summers will expand and winters will become less and less cold'.
Are we prepared?
"Unfortunately not. Even Italy has a Climate Change Adaptation Plan that is basically still in the drawers of the ministry. People don't know anything, while we should all be perfectly aware of what is happening. Also because the Mediterranean is one of the areas in the world most exposed to climate change. Here, then, there is everything: the glaciers in the Alps, which lost 6 per cent of ice in the summer of last year alone, forest fires, droughts, floods, and the rise in sea levels that threatens Venice (which risks having almost a metre more of sea at the end of the century) and the Po delta. A gigantic problem, because it is permanent. And the Mose will serve for a few decades, but it will not be able to cope with increases of this magnitude. The Paris Agreement says one thing very clearly: if we reduce emissions to zero by 2050, the temperature increase over pre-industrial levels will stop at 2 degrees, if we do nothing it will continue up to 5 by 2100. We cannot turn back, but we can reduce future damage and avoid going beyond 2 degrees, because that would condemn future generations to live on a hostile planet'.

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