2021 Nobel Prize Lectures in Physics

The three lectures examine how physical theory can make sense of complex systems with fluctuations and many interacting components. Syukuro Manabe describes the construction of climate models that connect atmospheric radiation, heat transport and carbon dioxide to changes in surface temperature. Klaus Hasselmann addresses the relationship between short-term weather variability and long-term climate, including methods for distinguishing human influence from natural variation. Giorgio Parisi examines disordered systems and the coexistence of multiple equilibria, with spin glasses providing a central setting for understanding apparently irregular collective behaviour. The programme preserves both parts of the prize: quantitative climate science and the statistical physics of disorder, rather than treating either as a substitute for the other.