“Today's climate is like a rigged deck of cards,” says Timothy Palmer

“Today's climate is like a rigged deck of cards

Abnormal heat waves, fires, droughts, floods, floods, avalanches. Experts call them "extreme events". In reality they are tragedies that have a very high cost in terms of human lives and biodiversity. All sharing the same trademark: they are attributable, more or less directly, to the climate changes taking place on the planet, in turn linked to human activity, and in particular to the release of climate-altering gases into the atmosphere. An issue on which the scientific community has now reached an almost unanimous consensus, and whose dynamics have been the subject of study for several decades: an effort that received its recognition with the awarding of the Nobel Prize in Physics in 2021 to Sukuro Manabe, Klaus Hasselmann and Giorgio Parisi precisely for their works on complex systems and climate change.

Scientific consensus on the anthropic origin of climate change. Image: University of Queensland, John Garrett

Among the researchers who have distinguished themselves in the field, Timothy Palmer, a physicist at the University of Oxford, one of the world's leading experts in non-linearity and dynamics of climate system. Palmer will be in Italy next week, on the occasion of the symposium for the centenary of the International Union of Pure and Applied Physics (Iupap) scheduled in Trieste from 11 to 13 July. It was an opportunity to reach Timothy Palmer and let us tell you a little more about this crazy climate.

Image: Timothy Palmer, University of Oxford

Fisher Studios Professor Palmer, how it has changed over the course weather our ability to predict the evolution of the climate? And why?

"The 'revolution' in the field of climate models took place between the 1960s and 1970s, when the team of Syukuro Manabe, Nobel Prize in Physics 2021, developed models that explained the interaction between the balance of solar radiation and the vertical transport of water masses due to convection. These models predicted not only the 'trivial' increase in the average surface temperature of the Earth, which would actually also have been explained by mechanisms that did not involve greenhouse gas emissions by humans - for example, an increase in solar activity -, but also two other phenomena: the cooling of the stratosphere and the more marked warming of the Arctic region. Phenomena that have occurred on time, which confirms the goodness of Manabe's models. In the following years there have been further improvements, mainly thanks to two elements: the collection of increasingly precise satellite data and the advent of supercomputers. In this way it was possible on the one hand to have a more precise set of initial conditions to be fed to the models, and on the other hand, a computing power that made it possible to solve the equations of the models with an ever greater spatial resolution. The same happened with the weather forecast: in the seventies it was possible to make forecasts for the next 48 hours at the most, now we can 'see' even up to a week. However, there is still a lot to do: we need to become even better, especially in improving the spatial resolution of the models, in order to have forecasts on a regional and local scale. My work focuses precisely on this. ”

Climate science is based on the concept of“ non-linearity ”. Can you tell us what it is?

"All phenomena in which the output does not vary proportionally to the variation of the input are non-linear. Let me explain with an example: if you won a million euros in the lottery, you would probably be very happy. If she won ten, she would be even happier, but not ten times happier: happiness is a non-linear phenomenon. The same goes for the climate, and that's what makes things very complicated. Doubling the concentration of carbon dioxide in the atmosphere does not lead, for example, to a doubling of the temperature: the relationship is more complex. To make things even more difficult is the fact that the climate system is a complex system, that is, a system in which a small variation of the initial conditions corresponds to a large variation of the system after a certain period of time. This makes it difficult to make 'punctual' forecasts, even if statistics allow us to macroscopically predict the trend of the climate, as a whole ".

One of the most common mistakes is to confuse the weather with the climate - also because the Italian language, unlike English, does not distinguish between weather and climate. I remember a tweet from Donald Trump in which, complaining about the harsh cold of a few winters ago, he sarcastically asked for an early return of global warming. Does he help us understand the difference between the two?

“I will answer you, once again, with an example. Suppose you have a deck of cards and shuffle them in order to have a completely random sequence. Now suppose you flip through the deck, and each red card corresponds to a hotter than normal day and each black card to a colder than normal day. Certainly we would not be surprised to have, from time to time, sequences of two, three, four or more red or black cards: repeating the browse of the deck a large enough number of times, we would still find a frequency of 50% for each color. However, if ten black cards are removed from the deck, the situation changes: it may still happen that you come across a long sequence of black cards, but by repeating the experiment you will notice an anomaly compared to a normal deck. Here: the single card is the weather, while the deck is the climate. And at the moment we are playing with a rigged deck. ”

What are the data that unequivocally show that the climate is changing and that it is not a“ fluctuation ”, as some argue?

“Certainly the global average temperature, which has remained stable for thousands of years and then, since the industrial revolution, has begun inexorably and incontrovertibly to rise. This is the reference figure for the scientific community. And then there is the anecdotal evidence of extreme events, which are increasingly frequent and increasingly extreme: last year in British Columbia, at very high latitudes, temperatures of 50 ° C were recorded. A large amount of ice has just disintegrated on the Marmolada, causing the tragedy we have all read about. And many other examples of this tenor could be made. It should be obvious to everyone that something strange, anomalous is happening. ”

Let's go back to climate models. How do they work? How reliable are they?

“Climate models are very complex. To simplify things, we can think that at the extremes of the spectrum there are the super-simplified models, which serve to corroborate or disprove the hypotheses of the theory, and the super-complex ones, which give quantitative and precise answers, but whose solution requires a lot. time and a lot of computational power. It is the so-called 'hierarchy of models': with the first models we try to understand which variables are important and which ones we can neglect; with the latter we simulate the evolution of the climate using only the important variables ".

What scenarios do they foresee for the future?

“It all depends on how rapidly the concentrations of carbon dioxide in the atmosphere will increase, a variable which, of course, the models cannot predict. In the scenario in which we were to continue to put carbon dioxide into the atmosphere, a further increase in temperature is expected in the next century, even up to 4 degrees more. It would be a catastrophe: the seas would rise, submerging many coastal cities; desertification, drought and the other extreme events we have talked about would increase; entire populations would be forced to move elsewhere. In short, nothing good ”.