Thursday, January 27

Climate change: the most influential climate research of all time (and just won the Nobel 54 years later)

After World War II, many of Japan’s best scientists found work in laboratories in the United States.

Syukuro (Suki) Manabe, a 27-year-old physicist, was part of this brain drain. He was working on weather forecasting, but left Japan in 1958 to join a new research project for the United States Weather Service.

The goal was to develop a numerical model that could be used to study the climate.

Working alongside Joseph Smagorinsky, the visionary first director of the Geophysical Laboratory of Fluid Dynamics, Manabe led a team of computer programmers to add missing physics to laboratory weather models.

Even the best computers in the world at that time were much less powerful than today’s mobile phones.

For the model to work, Manabe needed to make physics as simple as possible. This meant making a series of coding approaches to quantify how air exchanged heat and water vapor with land, ocean, and ice.

Thank you Manabe
At the age of 90, Manabe continues to work as a climatologist at Princeton University in the United States. (Photo: REUTERS)

This development of a climate model, the first of its kind, it was an ambitious 20-year project that finally earned him to Manabe a part of the 2021 Nobel Prize in Physics.

The key article arrived in the middle of this period: Manabe y Wetherald (1967).


Manabe is typically unassuming about the intentions behind his study. And when reading the title, “Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity”, many might think that it is even a bit boring.

However, the Nobel committee, myself, and the hundreds of colleagues around the world who voted for this work as the most influential climate science study of all time, we have a very different opinion.

In trying to simplify the code, Manabe and his colleague Richard Wetherald wanted to know the minimum number of discrete levels to use in their model atmosphere.

They also wanted to know which greenhouse gases needed to be included in the model to properly represent the way temperatures vary with altitude, as these gases absorb heat emitted from the Earth’s surface, but at different levels.

His three-dimensional climate model was too complex for computers at the time, so it was necessary to build a simpler one-dimensional model.

Manabe and Whetherald wanted to simulate how radiation and clouds interact to redistribute heat and water vapor through the atmosphere.

Most of the study is concerned with building the simple model and performing these tests. But they also detail two other experiments to quantify how greenhouse gases could alter the climate.

Thank you Manabe
“The physics of his models were fascinatingly simple.” (Photo: EPA)

And this is where the breakthrough came: they found they had built the perfect model for accurately estimate how human activities might alter the Earth’s surface temperature.

Valid estimates

His first climate change experiment of this type did not focus on analyzing the role of carbon dioxide, but on the effects of water vapor injected into the stratosphere from a possible fleet of supersonic aircraft, since these and a possible nuclear winter were the immediate concerns of the time.

However, Table 5 of the study went down in history as the first solid estimate of how much the planet would warm if carbon dioxide concentrations doubled. Manabe and Wetherald estimated 2.36 ℃ of warming, not far from the current best estimate of 3 ℃.

Previous attempts to estimate warming from increased carbon dioxide had failed as scientists struggled to understand how water vapor, the most important greenhouse gas in the atmosphere, would respond as the Earth warmed.

Manabe and Wetherald’s simple model could accurately redistribute water vapor like real clouds do, with a wide increase in water vapor concentration up to a certain humidity level.

This increase was found to amplify carbon dioxide heating by approximately 75%. This water vapor feedback estimate has also stood the test of time.

Manabe, in collaboration with several colleagues, went on to write many more fundamental studies on climate models. He laid the foundation for current global climate modeling efforts.

The physics was fascinatingly simple, so their models could run on early computers. However, being a simple model, the results could be understood and verified.

Thank you Manabe
The models created by Manabe had to be simple to adapt to the computers of the time, which were less powerful than a current cell phone. (Photo: REUTERS)

The way that Manabe applied these simple models to urgent problems it was revealing.

After graduating with a degree in physics more than 30 years ago, I chose a career in atmospheric sciences rather than particle physics.

I was always concerned about how my colleagues in conventional physics would view my applied physics.

Having a Nobel Prize in physics in our discipline gives me and my climate modeling colleagues the credibility and recognition we have longed for: climate science is real science.

* This article was originally published on The Conversation. You can read the original version here.

Piers Forster is professor of the physics of climate change and director of the Priestley International Center on Climate at the University of Leeds in England.

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