2021 Nobel Prize in Physics recognizes scientists who modeled Earth's climate and other complex systems

The 2021 Nobel Prize in Physics has been awarded to three scientists for their contributions to understanding complex systems, including Earth’s climate.

Half the approximately $1.1 million prize was awarded to Syukuro Manabe of Princeton University and Klaus Hasselmann of the Max Planck Institute for Meteorology, Hamburg, for “physical modelling of Earth’s climate, quantifying variability, and reliably predicting global warming.” Their work has led to development of the computational models that explain observed climate-change data and can predict future outcomes based on ocean phenomena, carbon cycles, human activities, and other interrelated variables.

The other half was awarded to Giorgio Parisi of Sapienza University of Rome for his discovery “of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales.”

In the 1960s, Manabe showed that increased concentrations of carbon dioxide in the atmosphere lead to increased temperatures at the Earth’s surface. Roughly 10 years later, Hasselmann developed computational methods that established the accuracy of early climate models despite the seemingly chaotic and variable nature of weather. Parisi, who studied disordered complex materials, developed mathematical techniques for uncovering hidden structure and patterns in systems that appear highly random.

At the Nobel Prize press conference today in Stockholm, John Wettlaufer, an earth and planetary sciences specialist at Yale University, remarked that understanding highly complex phenomena such as climate change requires looking at many individual complicated mechanisms and figuring out how to knit them together to make accurate predictions. That’s what this years’ physics Nobel laureates are being recognized for, he explained.

“I am truly delighted by this years’ physics prize,” says Eystein Jansen, a climate expert at the University of Bergen, in an email. These researchers “are true pioneers in developing models to simulate the climate system, its physics, and interlinkages.” Their work began with models that addressed key aspects of atmosphere dynamics and the way human activities can affect the climate, Jansen says. These scientists’ contributions have now been developed into the complex Earth System Models that incorporate the ocean, vegetation, carbon cycle, aerosols, and other global biogeochemical cycles to predict future scenarios. These models are used by researchers worldwide to understand the science of climate change.

“Our current understanding and concern with climate change hinges on the developments originating from their work," Jansen says, adding that it has led to important benefits for humanity and climate agreements such as the Paris Accord.

Sir Brian Hoskins, a climate-change scientist at Imperial College London has known Manabe and Hasselmann since the 1970s. In addition to praising these researchers for their groundbreaking work, he notes in an email that “both men were very encouraging to young scientists and inspirational to their colleagues around the world.”