This year’s Nobel Prize in Physics goes to three researchers to whom we owe fundamental knowledge about complex systems – including our climate. The US physicist Syukuro Manabe and Klaus Hasselmann, a researcher at the Max Planck Institute for Meteorology in Hamburg, laid the basis for today’s climate models: Manabe was the first to develop a model that showed the greenhouse effect of carbon dioxide. Hasselmann discovered a way to identify long-term climate trends and the anthropogenic influence despite short-term and chaotic weather fluctuations. The second half of the Nobel Prize goes to the Italian physicist Giorgio Parisi, who mathematically described the laws of complex, disordered systems such as glass.
Today, climate research and many other disciplines of physics can no longer be imagined without them: Numerical modeling is one of the most important tools in science when it comes to researching and describing complex systems. Such systems – from the accumulation of tiny particles in a gas to the planet-spanning interactions of the Earth system – are characterized by a multitude of chaotic, non-linear processes, but nevertheless follow certain laws and trends. For example, it is almost impossible to predict whether it will rain in four weeks’ time or the sun will shine – the weather is too changeable and even the smallest of influences can cause changes that are difficult to predict. On the other hand, however, one can certainly determine how the climate in November has developed over the last few decades and what the mean temperatures are usually in a location in this month.
The complex climate in the model
Two of this year’s Nobel laureates in physics laid the foundations for how to record and reproduce the climate and its complex interactions in models and analyzes. Originally from Japan, Syukuro Manabe left Tokyo in the 1950s to continue his research career in the United States. There, in the 1960s, he worked on a physical model that was supposed to map and specify a connection that was recognized by the physicist Svante Arrhenius at the beginning of the 20th century: the greenhouse effect. Arrhenius had already recognized that the absorption of radiation by gases in the earth’s atmosphere plays an important role in the radiation balance and thus the climate. But which gases contributed how much and how was unclear.
This is where Manabe started. In order to better handle the enormous complexity of the processes, he began with a greatly reduced model that only looked at one-dimensional, 40-kilometer-high columns of the atmosphere, their gases and their interaction with radiation. By varying the gas content and increasingly precise mathematical-physical descriptions of atmospheric processes such as convection currents in the air or the contribution of humidity and temperature, Manabe and his colleagues succeeded in developing a physical model of the earth’s atmosphere and its climate reactions for the first time. With it they determined the climate sensitivity for the first time – the extent to which the temperature reacts to an increase in CO2 values. Based on these findings, Manabe published the first three-dimensional General Circulation Model (GCM) in 1975 – the first global climate model.
The second award winner, Klaus Hasselmann from the Max Planck Institute for Meteorology in Hamburg, tackled another crucial problem in climate modeling about ten years later: the relationship between weather and climate. Because the chaotic weather conditions, which fluctuate on very different time scales, make it difficult to identify long-term climate trends and possible influencing factors for these trends. Hasselmann developed a method to include the “background noise” in the models. This made it possible to reconstruct how all weather events shape our climate. Building on this knowledge, the scientist also found a way to identify the “fingerprint” of individual factors on the climate system. Only through this further development is it possible to quantify the anthropogenic contribution to climate events. “In the spirit of Alfred Nobel, Syukuro Manabe and Klaus Hasselmann have contributed to the good of mankind by giving our knowledge of the earth’s climate a solid physical basis,” said the Nobel Foundation.
Spin glass and frustrated atoms
The second half of this year’s Nobel Prize in Physics goes to the Italian researcher Giorgio Parisi, who has dealt with equally complex systems – only on a much smaller scale. In his work on complex materials, the physicist initially focused primarily on the so-called spin glass. This is a special metal alloy in which, for example, some iron atoms are scattered in a lattice of copper atoms. Strangely enough, even these few foreign atoms ensure that the metal radically changes its magnetic properties. This is due to the “frustrated” interactions of the atomic spins – the intrinsic angular momentum of the individual particles. Due to the presence of the foreign atoms, the spins of the metal atoms can no longer align themselves in an orderly manner, because contradicting influencing factors act on them.
Parisi was the first to succeed in mathematically describing the physics behind these interactions – and thus laid the basis for the description of spin glass and many other complex, disordered systems. His findings are therefore not only important for physics and materials research, but also for mathematics, biology, neuroscience and computer technology, as the Nobel Prize Committee explains. “His discoveries are among the most important contributions to the theory of complex systems,” said the committee.
Source: Nobelprize.org