A swallow does not make spring. And not even a momentary anomalous "heat" in January means that we can speak of a winter with above-average temperatures. On the contrary, according to the numbers, the month of December was colder than the average: “Especially in the North, where there were abundant and frequent snowfalls, but also in the Centre-South: overall, in Italy there were temperatures below the average for values between half a degree and one degree,” explains the meteorologist Raffaele Salerno of the Epson Meteo Center. Almost one degree less is a lot, on average, as are the many 0.7-0.8 degrees above average that have characterized recent years, especially since 2010, since global warming has caused a constant "positive climatic anomaly" ( this is the name of the climatic difference with the plus sign compared to the mean).
Therefore, let the practically spring-like temperatures of the past few days not deceive, with a maximum of 20 degrees in Rome or the minimum around 10 degrees recorded in Milan (“an absolutely exceptional event”): so far this winter has been cold, normal or even below, and certainly colder than the last two, when despite the intense waves of frost especially in January 2017, the winter period – which meteorologically is considered in the December-January-February quarter – was above average. But what would the average be and how is it calculated? “The average – explains Salerno – is calculated by examining the temperatures of the thirty years 1981-2010: compared to the data that emerges, the years from the mid-90s onwards are hotter, in particular after 2010, while the first half of the period in question sees almost all years below those values, both globally and in Italy”.
Indisputable confirmation that global warming exists and has accelerated its effects in the last few yearseven more so if we consider that the averages for the thirty years 1981-2010 are higher than those for the period 1971-2000, which are in turn higher than those for 1961-1990 and so on. Is it only the fault of global warming or also of the climatic phases that the planet physiologically experiences? “Surely the Earth has climatic phases independent of the human factor, but the hand of man is necessarily there, if we think that in the last million years, since the planet has had this conformation and it makes sense to make comparisons, the temperatures they had never been so high. Not even in the Middle Ages, when there was a warmer phase for a few centuries, followed by a particularly cold phase between the mid-1500s and mid-1800s”.
The industrial phase then produced an increase of about 1 degree within 150 years, with an acceleration in recent decades: a lot, with serious dangers for the ecosystem, even if the data is not homogeneous. “The areas with the most significant increase – reveals the meteorologist of the Epson Center – are the polar and subpolar arctic ones, and also Europe. But there are also areas where the values go against the trend and where negative anomalies have been recorded in recent years, i.e. a downward trend: for example in Antarctica it is colder, and if we look at 2017 also in some regions of North Africa". Just a few days ago are, among other things, the images of an unusual snowfall in the Sahara desert. In short, it is a little warmer, also but not always and not everywhere: if in fact in Russia the anomalous temperatures have led to a lack of snow, North America has recently experienced a practically glacial phase and even in Italy it was colder than it should have been.
In perspective, how can this winter be defined? “So far – replies Salerno – it has been colder in December and slightly milder in these first days of January, therefore overall in the norm, which is already something compared to the trends of recent years. In the next few days, colder air will certainly return while the projections for the next few months, which must be taken with a grain of salt because they can easily make mistakes, indicate a slightly milder winter ending but an early spring, in the months of March and April , normal or slightly below. In short, the first months of 2018 do not allow us to think, for now, of particular anomalies".
