The record heat of these days has brought back into circulation one of the most enduring expressions of recent years. It resists heat waves, statistics, maps, and even its cousin who “did his own research.” The expression is: “Even forty years ago it was hot.” It is an interesting expression. Not because it is untrue. In fact, it is true. Even forty years ago there were scorching summers. There were temperature records. There were even sudden hailstorms and floods. The problem is another. This expression seems to have come out of a 19th-century textbook, while climate is a problem that belongs to 21st-century physics. Whoever says this sentence imagines climate as a giant thermometer: the temperature rises a little, then falls a little. Every heat wave is followed by a cold period. If something similar has happened today, then there is nothing new.
But climate is not a thermometer. It is one of the most complex systems we know. And this is where common sense begins to betray us. Ready-made expressions, clichés, come into play. The most common is: “Oh, it’s always been hot.” Or its close cousin: “It was even worse in 1983.” And, of course, the Olympic champion in this category: “There used to be a mid-season.”
The latter, by the way, is probably the only climate theory that has survived for decades without ever publishing a scientific article. Fortunately, physics exists. It is much less spectacular than clichés, but it explains the world much better. For centuries, we have been accustomed to thinking in linear terms. If I double a force, I expect to get twice the effect. If I increase a cause a little, I expect a slightly larger effect. But nature has never signed this agreement. Complex systems work differently. They are made up of millions of elements that constantly interact: the atmosphere, the oceans, the currents, the ice, the vegetation, the clouds. None of them decides alone. Yet all of them together create something that does not belong to any particular element.
Scorching heat and physical emergencies
In physics, this phenomenon is called an emergency. And this is where the “even forty years ago…” reasoning begins to break down. Because it confuses a single event with the way the entire system behaves. Let’s take an example. Imagine rolling a pair of dice. It comes up a six. You roll it again. It comes up a six again. It can happen. You roll it a thousand times, and sixes keep coming up almost twice as often as they should. At this point, no physicist would say, “Well, it came up a six before.”
It would mean something entirely different: The probability distribution has changed. And that’s exactly what we’re seeing with climate. It’s not the record today that’s telling us anything. It’s the fact that records are happening more and more often. That they’re being broken by ever-greater margins. That they last longer. That they appear simultaneously in different Regions of the planet. Many people imagine global warming as a kind of elevator. The average temperature rises by a degree or two, and everything else follows suit. That’s not how it works. If it were an elevator, at least there would be a button to go back to the ground floor. Think of the classic bell curve, which describes many natural phenomena. Most events are concentrated near the average. Extreme events are at the ends of the curve.
If this curve shifts even slightly to the right, extreme events increase much more than the shift itself would suggest. A small change in the average is enough for the probability of the rarest events to increase dramatically. This is mathematics, not ideology. But there is more to it. Because climate is not just statistics. It is a dynamic system. And in complex systems there are feedback mechanisms.
The earth heats up. It loses moisture. A dry earth evaporates less water. By evaporating less, it removes less heat from the environment. Therefore, it heats up even more. The more it heats up, the more it dries up. The more it dries up, the more it heats up. It’s a vicious cycle that feeds itself. The same thing happens with the stability of anticyclones, with some atmospheric currents, and with the transport of moisture. When these interactions start to reinforce each other, the system no longer responds proportionally. It changes the way it behaves. And that’s the key word: Behavior.
THE SYSTEM IS CHANGING ITS WAY OF BEHAVIOR
Today we are not simply observing a few degrees higher. We are observing a system that is changing the way it works. The person who keeps repeating, “It used to be hot,” is actually describing the weather. Climatology studies climate. They are two completely different levels. It is like observing a single water molecule and believing you have understood a hurricane. The physics of complex systems teaches us that the most interesting properties do not belong to individual elements. They belong to the whole. Precisely for this reason, climate change denial often seems more like a methodological error than a matter of opinion.
It’s a bit like claiming to understand the stock market by following just one stock. Or Milan traffic by looking at just one car.
The mental model turns out to be wrong. And when the model is wrong, the conclusions may seem reasonable. But they remain wrong. For centuries we have thought that climate was, above all, a matter of temperature. Temperature is what we feel on our skin. Physics, on the other hand, looks at energy. Because when the energy balance changes, the way the system evolves also changes. Climate is no exception. Heat waves, prolonged droughts, and extreme events are symptoms. They are the traces left by a system that has begun to behave differently. And this is where physics becomes practical. When a system approaches a critical threshold, you don’t keep feeding it in the hope that it will return to its previous state on its own. Instead, you try to reduce the cause that continues to increase the energy of the system.
That’s why today we’re talking about decarbonization, about energy efficiency, about all the technologies that can reduce emissions, from next-generation nuclear power to renewables. Not because some politician says so. But because that’s what a thermodynamicist would say.
These represent the rational and measurable effort to change the energy balance of the system. That’s why I keep smiling when I hear people say, “It was hot even forty years ago.” Okay. But how much more energy is the climate system storing today compared to forty years ago? Because it is precisely the energy variable that determines the future evolution of the system. We can continue to debate heat and continue to reason as we did in the eighties. Meanwhile, the Earth responds to the energy that the climate system stores, thanks to us. And there is no nostalgia that can convince it to behave differently. (Corriere della Sera)