Syukuro Manabe, pioneer of the science of global warming – Nikkei Asia
TOKYO — The physical modeling of Earth’s climate, for which Syukuro Manabe, senior meteorologist at Princeton University, was chosen as a recipient of the 2021 Nobel Prize in physics is a technology to simulate physical phenomena of the Earth on a computer. Aiming to create a “digital twin” of the real world, it is an indispensable tool for discussing plans for humanity’s future, such as predictions on global warming and the effects of measures against it.
Meteorological modeling has developed from a simple primary model of reproducing behaviors of atmospheric columns from the ground to the sky, to a general circulation model calculating three-dimensional atmospheric circulation, to a coupled ocean-atmosphere model combining the general circulation model with one for the ocean. Manabe has been involved in all of these as a pioneer.
Manabe went to the U.S. in 1958 and conducted studies on the primary model together with his colleagues at the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration. Joseph Smagorinsky, the first head of the GFDL, and Kirk Bryan, an oceanographer at the GFDL, were his principal research partners for the general circulation and ocean-atmosphere models, respectively.
Global meteorological modeling divides the atmosphere and oceans into box-like sections and calculates temperature, wind speed and current speed in each box. Referring to the ocean-atmosphere model, Manabe said, “Oceanic currents and pressure patterns exactly like those on the globe appear when a program is operated after setting conditions.”
The modeling was initially used mainly as an experimental method of studying meteorological mechanisms. When the density of carbon dioxide and other greenhouse gases in the atmosphere increases, temperature rises because they absorb infrared light from the surface that otherwise would carry its energy into space, and also radiate some of that heat back to Earth.
Manabe and his colleagues studied temperature changes in situations such as a doubling of the carbon dioxide in the atmosphere. They also tested how well an ocean-atmosphere model capable of making long-term simulations could reproduce known past weather.
The modeling then began to be used for predicting the future of the planet. James Hansen, a researcher at the National Aeronautics and Space Administration, drew global attention in 1988 when he told the U.S. Congress that it was “99% certain” that global warming was caused by human activities. Hansen’s view was based on a scenario of rapid warming calculated using his own meteorological model.
The initial model developed by Manabe and his partners had a low definition of around 500 km. But the current model has a definition of 100 km for the globe as a whole and several to tens of kilometers in specific regions. Drastic advances in computing speeds have made detailed simulations possible.
The current model is capable of incorporating the surface of the land, in addition to the atmosphere and oceans, plus the movements of fine particles and chemical substances in the atmosphere. There also are attempts to include human behavioral changes such population movements and logging. The work to create a global digital twin that Manabe launched keeps advancing.