Climate change

The man who predicted climate change


In late 1966, in the sprawling computer lab of the Washington, DC office building that housed the United States Meteorological Bureau, Syukuro Manabe was waiting for a print job to finish. The stake was the fate of the planet. Manabe, who was thirty-five, had come to the United States from Japan almost a decade earlier. He led a team of computer programmers tasked with building a mathematical simulation of the planet’s atmosphere. It had taken years to perfect it and cost millions of dollars. The simulation was now over.

Syukuro Manabe’s models were among the first to reliably assess the effects of increasing CO2 in the atmosphere.Photo courtesy of the Geophysical Fluid Dynamics Laboratory

With an alarming click, the printer came alive and a single continuous sheet, striped in light green and white, unwound on the floor. The IBM 1403 could print six hundred lines per minute, but Manabe couldn’t stand the noise it made and usually avoided it when going out to lunch. This job couldn’t wait. If successful, Manabe’s simulation would quantify, for the first time, the relationship between carbon dioxide and the temperature of the Earth’s atmosphere.

The fact that the earth’s atmosphere retains heat from the sun has been understood since the beginning of the 19th century. Water vapor was the primary driver, trapping thermal energy at low altitudes and warming the planet’s surface by about sixty degrees Fahrenheit. (If Earth had no atmosphere, its surface temperature would average zero degrees Fahrenheit.) The open question was whether other atmospheric gases contributed to this greenhouse effect. Carbon dioxide was thought to have an effect, but it was only three parts per ten thousand of the Earth’s atmosphere by volume. The researchers wondered if its impact was detectable.

Manabe assumed it was. Three games for ten thousand wasn’t much, but even a trace of gas, with the right properties, could have a disproportionate impact. Without carbon dioxide, there would be no photosynthesis and almost everything on the planet would die. Perhaps shifting carbon dioxide levels the other way – as burning fossil fuels did – would have an equally catastrophic effect.

There was no direct way to test this hypothesis; Manabe, who lived on Earth, did not have access to another disposable planet on which to conduct experiments. Instead, he had to simulate the effects of atmospheric change from basic thermodynamic equations. For the surface of the planet, these equations could be done by hand, but once additional atmospheric layers were added the calculations became more complex.

Fortunately, Manabe had access to a machine called Stretch, one of the most powerful computers ever built. Officially, it was an IBM 7030, designed, at the request of the Pentagon, to simulate the effects of the hydrogen bomb. Nine of these computers had been produced; others had been sent to the Los Alamos National Laboratory and the National Security Agency. The latter, after much pressure from the boss of Manabe, had been assigned to the weather forecast, to demonstrate to the public that computers could be useful. Stretch was larger than a single-family home and had sixty freestanding elements. The complete device weighed about thirty-five tons and was cooled by a studio-sized air conditioner.

Manabe had arrived in the United States in 1958; he had never left Japan and spoke little English. But he shared his colleagues’ fascination with computer technology, and, outfitted with the default sports coat and thin tie, he quickly fitted in. He was drawn to America’s informal social norms, which he preferred to the more hierarchical approach of Japan. “The hardest part was the western toilet,” Manabe told me last year. “I had never seen one before.”

Manabe eventually got a job at Princeton, where he lives today. Last week, at the age of ninety, he received the Nobel Prize in Physics. The award committee cited Manabe’s 1966 simulation as the first reliable prediction of climate change. The simulation included a plot of dots representing the sensitivity of the Earth’s temperature to carbon dioxide at different altitudes. The printer did not have the ability to fit a curve to the data, so for the last step Manabe had to draw it himself. “I used a pencil,” he says. “It took a long time.”

Manabe recently received the Nobel Prize in Physics.Photograph by Kyodo / AP

Manabe’s pencil chart revealed three unexpected results. First, according to the simulation, increasing carbon dioxide from three parts per ten thousand to six could lead to an increase in the average Earth’s surface temperature of more than four degrees Fahrenheit. A comparable temperature rise at the end of the last ice age had raised ocean levels by thirty meters.

Second, Manabe’s simulation predicted that carbon dioxide would trap thermal energy in the lower atmosphere. The Earth’s surface and its oceans would therefore become warmer, while the upper atmosphere would cool. This combination – colder at the top, warmer at the bottom – is now viewed by climatologists as the smoking gun of man-made climate change. (Other potential causes of global warming, such as the sun getting brighter, would warm the atmosphere evenly at each altitude.)

Finally, Manabe’s model implied that as the upper atmosphere cooled, it would warp, causing atmospheric boundaries to crumble. The 1966 pencil chart was the first glimpse of Earth’s future: the surface would bake, and the sky would crumble.

Syukuro Manabe was born in September 1931 on the island of Shikoku, south of the main island of Honshu. Her family lived in a remote mountain hamlet, where her father was the village doctor. On the day Manabe was three years old, Typhoon Muroto, then the deadliest storm in Japanese history, made landfall on Shikoku, destroying 30,000 homes and killing 3,000. Powerful cyclones captivated Manabe in his childhood. “I had a horrible memory and was awkward with my hands,” he told a Japanese newspaper. “My only good trait was to look at the sky.”

When Manabe was ten years old, the Japanese Navy bombed Pearl Harbor. In 1944, when he was thirteen, American forces launched one of the largest bombing campaigns in history against mainland Japan. Shikoku was not a target, but bombing convoys would fly over the island en route to Honshu. While his classmates were hiding in bomb shelters, Manabe was studying for his exams. “Fortunately, the planes just flew over us, because we are in the countryside at the college,” he told an oral historian. Across the channel from Shikoku sat Hiroshima; one of the planes that flew over the island was the Enola Gay.

Manabe downplayed the impact of his wartime education. “The war didn’t bother me at all,” he said. “I continued to prepare for the entrance exam. But he recognized a long-term effect. “I didn’t grow as much as I should have,” he said. “I was malnourished all the time.” The post-war American occupation brought prosperity. In 1955, the Toyota Motor Corporation introduced its first mainstream car. As the middle class recovered, Japanese households sought to acquire the “Three Sacred Treasures”: a television, a refrigerator, and a washing machine. In the decades since the introduction of Western food products, the average height of an adult Japanese man has increased by almost four inches. These advances have been spurred by immense growth in the use of fossil fuels.

Manabe passed his entrance exam at the University of Tokyo. His brother, father, and grandfather were all doctors, but Manabe decided to be a physicist. “Then I realized I’m not very good at math to get into difficult physics,” he said. “I’m not very good at measuring things either. And I had given up on biology, because I’m not good at memorizing things. Manabe finished in meteorology.

He was a patient student. Struggling to keep up with some of his professors’ lectures, he learns meteorological physics at his own pace and has to retake at least one exam. But, when Manabe and his fellow graduates used these physical equations to predict the weather, he became one of the stars of the department. Without access to a computer, the students made calculations by hand on graph paper. “I spent hours drawing contour lines,” Manabe told me. He seemed nostalgic for the practice: “By drawing outlines yourself, you can start to notice things that you have never noticed before. Maybe this primitive process is good, in a way.