The Nobel Committee decided to split the 2021 Prize in Physics between three scientists.

The first part was awarded jointly to Germany’s Klaus Hasselman and the US Syukuro Manabe "for the physical modelling of Earth’s climate, quantifying variability and reliably predicting global warming."

The other half was given to the Italian theoretical physicist Giorgio Parisi "for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales."

Complex systems are chaotic and difficult to understand. This year’s award "recognizes new methods for describing them and predicting their long-term behavior."

The Earth's climate, as the Nobel Committee noted, is "one complex system of vital importance to humankind." Syukuro Manabe demonstrated how enhanced levels of carbon dioxide in the atmosphere lead to increased temperatures at the surface of our planet. "In the 1960s, he led the development of physical models of the Earth’s climate and was the first person to explore the interaction between radiation balance and the vertical transport of air masses. His work laid the foundation for the development of current climate models," the Royal Swedish Academy of Sciences said.

Ten years later, Klaus Hasselmann designed a model that brings together weather and climate, and thus answering the question of why climate models can be reliable, despite the variability and chaos of the weather. He also developed methods "for identifying specific signals, fingerprints, that both natural phenomena and human activities imprint in the climate." "His methods have been used to prove that the increased temperature in the atmosphere is due to human emissions of carbon dioxide," the Committee mentioned.

Giorgio Parisi discovered latent patterns in disordered complex materials around 1980. "His discoveries are among the most important contributions to the theory of complex systems. They make it possible to understand and describe many different and apparently entirely random materials and phenomena, not only in physics but also in other, very different areas, such as mathematics, biology, neuroscience and machine learning," the Swedish scientists noted.

The 2021 discoveries demonstrate that our knowledge about the climate rests on a solid scientific foundation, based on a rigorous analysis of observations, the Nobel Committee believes. "This year’s Laureates have all contributed to us gaining deeper insight into the properties and evolution of complex physical systems," Chair of the Nobel Committee for Physics Thors Hans Hansson stated.

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