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Finding hidden laws in complex systems

  Climate is a complex system with many variables, and it is very difficult to predict climate change. Japanese-American meteorologist Shuro Manabe and German meteorologist Klaus Hasselmann rose to the challenge and solved part of the puzzle of long-term climate prediction, for which they won the 2021 Nobel Prize in Physics. They were also awarded the prize by Italian physicist Giorgio Parisi, who studied the interplay between microscopic disorder and macroscopic order in complex systems, promoting the theoretical study and practical application of complex systems.
Solving the Prediction Conundrum of Global Warming

  As early as the first half of the 20th century, people realized that the global average temperature was gradually rising, that is, the problem of global warming. Later, scientists found that this was mainly caused by excessive carbon dioxide emissions caused by human activities.
  There are many factors affecting climate change, how to prove that carbon dioxide is the main factor causing global warming? Manabe Shurou and his colleague Richard Weatherd, using methods from physics, proved this conundrum. They built a radiative convection balance model to simulate the relationship between changes in atmospheric composition and changes in temperature. The model clearly shows that as the concentration of carbon dioxide in the atmosphere rises, the average global temperature will continue to rise. Using this model, Manabe Shuro predicted future global warming trends: for every doubling of carbon dioxide concentration in the atmosphere, the global average temperature would rise by 2.3°C.
  Manabe Shurou also discovered that carbon dioxide is mobile in the atmosphere. In other words, the increase in carbon dioxide emissions will not only hurt the emitters, but the world will follow. Manabe Shuro predicts, based on his own research model, that the polar regions are warming more than other regions. Later, his observations of glaciers in the North and South Poles confirmed this prediction. Therefore, if energy conservation and emission reduction are not implemented, people will not only suffer from more extreme weather due to global warming, but also lose coastal habitats due to rising sea levels.
The impact of human activities on global warming

  There have been many major global warming or cooling events in Earth’s history, even before humans appeared. Is the global warming event over the past 100 years really caused by human activities? There were many people who doubted this. And the results of Klaus Hasselmann’s research help to clear up doubts.
  There are many factors that affect climate change, some of which have different short-term and long-term effects. Although short-term weather forecasts are more accurate than long-term climate predictions, short-term weather changes are more chaotic than long-term climate changes. Therefore, to find the law of long-term climate change from short-term weather changes is equivalent to finding the direction of twine from a mess.
  Klaus Hasselmann found that changes in solar radiation, volcanic particles or greenhouse gas concentrations leave unique signals in meteorological systems that can be identified and that this identification method can also be applied to human activity Effects on the weather system. Klaus Hasselmann used this identification method to build a stochastic climate model that innovatively found patterns in complex weather systems. Stochastic climate models suggest that the increase in global average temperature is not a natural event, but the result of human activity, mainly increased carbon dioxide emissions.
Disorder and order in complex systems

  Manabe Shuro and Klaus Hasselmann’s research has led to an understanding of how complex systems such as climate work, while George Parisi’s research has led to an understanding of the macroscopic properties of complex systems.
  In 1980, George Parisi discovered hidden patterns in disordered and complex material. This disordered material is spin glass, which is not our usual glass, but a copper-iron alloy that exhibits a glassy state under special conditions. Although glassy substances are classified as solids, their properties are intermediate between solids and liquids. The iron atoms in the spin glass are randomly mixed into the crystal lattice of copper atoms, and the spin of the iron atoms generates a magnetic field, which makes the spin glass a magnetic material. The spin direction of iron atoms is disordered and random, but the magnetism exhibited by spin glass is specific and ordered.
  Through the study of spin glasses, George Parisi proposed the esoteric theory of “replica symmetry breaking”. In simple terms, it enables people to understand and describe the hidden laws behind the randomness of complex systems, and is one of George Parisi’s most important contributions to the theory of complex systems. The importance of this theory is manifested not only in the physics community, but also in many other seemingly unrelated fields, such as materials science, biology, neuroscience, and machine learning.

Climate is a complex system.

Manabe Shurou, Klaus Hasselmann and George Parisi (left to right)
Practical uses for complex systems research

  The research of the above three scientists shows that, for a complex system disturbed by microscopic disorder, the nature of macroscopic order can be found out by using reasonable statistical methods. Such research is not only of theoretical significance, but has practical application. For example, the weather forecast that we pay attention to every day is the prediction obtained by meteorologists after modeling the disordered phenomenon of atmospheric motion.
  The work of Shuro Manabe and Klaus Hasselmann is a good example of the combination of complex system theory and practical use (weather forecasting). Faced with more and more meteorological disasters such as high temperature and heat, rainstorms and floods, and super typhoons, people are more and more aware of the huge threat that climate change poses to human survival. When the government formulates relevant climate policies, it cannot just rely on people’s intuitive feelings, but must clarify the root causes of climate change, and then take corresponding measures in a targeted manner. The studies of Shuro Manabe and Klaus Hasselmann have shown the relationship between climate change and carbon dioxide emissions. Therefore, in recent years, governments and relevant organizations of the United Nations have vigorously advocated “carbon peaking” and “carbon neutrality”. “.
  Thors Hans Hansen, Chairman of the Nobel Prize in Physics Prize Committee and Academician of the Royal Swedish Academy of Sciences, emphasized: “The discovery of these three scientists has been recognized by the Prize Committee and shows that our understanding of climate is not only based on solid Scientifically based, and based on rigorous analysis of observations. Their discoveries help us gain a deeper understanding of the nature and evolution of complex physical systems.”
  We believe that with the continuous development of technology, people’s understanding of meteorology, materials, astronomy, etc The understanding of complex systems in the field will become deeper and deeper, and the ability of human beings to seek advantages and avoid disadvantages will become more and more powerful.

  Manabe Shuro, born in Japan in 1931, received a Ph.D. in Science from the University of Tokyo, Japan in 1958, and then worked for the US Weather Service, and is now working at Princeton University in the United States.
  Manabe Shuro has close contacts with Chinese meteorologists, and has exchanged lectures in my country many times. Academicians such as Ye Duzheng, Tao Shiyan and Zeng Qingcun of the Institute of Atmospheric Physics of the Chinese Academy of Sciences have worked with Shuro Manabe and forged a deep friendship with Shulang Manabe. Shuro Manabe and Academician Ye Duzheng also collaborated in research and published an academic paper on soil moisture memory in international journals in 1982, which promoted the international numerical simulation research on the climate impact of the Qinghai-Tibet Plateau.

  Klaus Hasselmann, born in Germany in 1931, received his Ph.D. from the University of Göttingen in Germany in 1957, and is currently the Vice-President of the European Climate Forum.
  Klaus Hasselmann’s interest in physics came from a radio. At 13, he bought a radio from a friend. “What impressed me was that I could hear great music through my headphones even when it wasn’t plugged in,” he said. At the time, he wanted to better understand this confusing phenomenon, so he went to the library to learn about it. physical knowledge.

  Giorgio Parisi, born in Rome, Italy in 1948, received his Ph.D. degree from the University of Rome, Italy in 1970. He is currently a professor at the Department of Theoretical Physics at Sapienza University in Rome, Italy, and a researcher at the Italian National Institute of Nuclear Physics.
  George Parisi’s grandfather and father were both construction workers and had hoped that George Parisi would become an engineer. But George Parisi read a lot of popular science books at an early age and developed an interest in basic science. In college, he had to choose between physics research and mathematics research, but he was attracted by the brilliant achievements of physics at that time and chose physics. His research interests are very broad, and he has made many decisive contributions in the fields of physics such as particle physics, statistical mechanics, fluid dynamics, condensates, supercomputers, etc., and has been widely recognized; he also uses the methods of physics to engage in biology Research and published academic papers on neural networks, the immune system, and animal population movements.

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