Nobel Prize 2021: How Complex Systems, Like Earth’s Climate, Work — Research That Won Physics Nobel | EXPLAINED
This year's Nobel Prize in Physics has been awarded to Syukuro Manabe, Klaus Hasselmann, and Giorgio Parisi for groundbreaking contributions to our understanding of complex physical systems’
New Delhi: The Royal Swedish Academy of Sciences has awarded the 2021 Nobel Prize in Physics to Syukuro Manabe, Klaus Hasselmann, and Giorgio Parisi, "for groundbreaking contributions to our understanding of complex physical systems”.
One half of the prize has been jointly awarded to Manabe and Hasselmann "for the physical modelling of Earth's climate, quantifying variability and reliably predicting global warming". The other half has been awarded to Giorgio Parisi "for the discovery of the interplay of disorder and fluctuations in physical systems from atomic to planetary scales".
“They have laid the foundation of our knowledge of the Earth’s climate and how humanity influences it, as well as revolutionzed the theory of disordered materials and random processes,” the academy said.
This year's Nobel Prize in Physics recognises new methods for describing complex systems such as Earth's climate, and predicting their long-term behaviour.
Pioneers Of Climate Models
Manabe demonstrated how increased levels of atmospheric carbon dioxide increases temperatures at the surface of the Earth. He led the development of the physical models in the 1960s. Current climate models are based on Manabe's work.
Hasselmann created a model linking weather and climate, about 10 years after Manabe's work. He devised methods for identifying “fingerprints” imprinted in the climate — that is, which processes are natural and which are caused by humans. Studies have used his methods to prove that human emissions of carbon dioxide result in increased atmospheric temperature.
Thus, the foundation of our knowledge of Earth's climate and the influence of humanity on it was laid by the pioneering work of Manabe and Hasselmann’s climate models.
Complex Systems
Around 1980, Parisi discovered hidden patterns in disordered complex materials. He made revolutionary contributions to the theory of disordered and random phenomena, and provided theoretical solutions. Climate and weather are examples of complex systems.
During the Nobel Prize press conference, Parisi said, "It's clear that for the future generation, we have to act now in a very fast way."
Different interacting parts constitute complex systems, which may have a large number of components, making it difficult to describe them mathematically. From the discoveries of this year's Nobel laureates in physics, scientists have obtained a greater knowledge of such systems, and about their long-term development.
Syukuro Manabe's model
In the 1950s, Manabe conducted research to understand how increased levels of carbon-dioxide resulted in increased temperatures. He was the first researcher to explore the interaction between radiation balance and the vertical transport of air masses because of convection. He also considered the heat added by the water cycle.
Manabe's model also found that hot air, being lighter, rises up through convection, and carries water vapour along with it, which results in the formation of clouds when the atmosphere is colder, and latent heat stored in the water vapour is released.
His model confirmed that increased levels of carbon-dioxide result in temperature variations, and that solar radiations are not responsible for increasing the temperature. From the insights of this one-dimensional model, Manabe created a three-dimensional climate model and published it in 1975.
Klaus Hasselmann's Research
About 10 years after Manabe's work, Hasselmann found a link between weather and climate. The uneven distribution of solar radiation results in rapid changes in Earth's weather. Colossal transports of heat occur between different latitudes, between ocean and land, and between higher and lower air masses. This colossal transport of heat drives the weather on the Earth.
As a result of Hasselmann’s work in the 1980s, weather forecasts could be made on the basis of a strong scientific foundation.
Hasselmann also developed methods to identify human impact on the climate system. Therefore, Hasselmann's models helped him distinguish between natural and human causes of atmospheric heating. Over the years, several researchers have made use of his climatic models. One important finding is that the world has heated by 1°C over the past 150 years.
Giorgio Parisi's Discovery
Around 1980, Parisi presented the discovery that hidden rules govern random phenomena. In his original work, he used spin glass. Spin glass is a special type of metal alloy in which iron atoms are randomly mixed into a grid of copper atoms. The iron atoms result in puzzling changes in the material's magnetic properties. Unlike an ordinary magnet, the spins in a spin glass do not point in the same direction, but are frustrated, which means that some point in the same direction while others point in the opposite direction.
In 1979, Parisi made a decisive breakthrough when he demonstrated a solution to the spin glass problem. He discovered a hidden structure in such complex disordered systems, and used mathematics to describe the complexity. His theory of disordered and random phenomena covers many other complex systems.
Parisi's discoveries about the structure of spin glasses are applied in fields such as biology, machine learning, and neuroscience. He has also studied other phenomena such as the patterns arising in clusters of starlings, which are governed by random processes.
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