From the Princeton Weekly Bulletin October 13, 1997
Greenhouse effect "godfather"
retires
By Mary Caffrey
Syukuro Manabe
didn't coin the phrase "greenhouse effect," but without him, it might
not be a household expression.
On September 29, Manabe, senior
scientist with the Geophysical Fluid Dynamics Lab and lecturer with
rank of professor in the Atmospheric and Oceanic Sciences Program,
retired from GFDL after nearly 30 years at Princeton. Manabe, who has
been described by colleagues as the "god-father" of the greenhouse
effect, capped his GFDL career by winning the 1997 Volvo
Environmental Prize, a $200,000 award that he will
split with V. Ramanathan, senior scientist at Scripps Institute of
Oceanography in LaJolla, Calif. The two will receive their award
October 21 in Brussels.
Manabe is a pioneer in the field of
climate dynamics, having developed the first mathematical models of
the atmosphere and later coupled models of the atmosphere and ocean.
Since starting his career in Washington, D.C., in 1958 at the U.S.
Weather Bureau, Manabe has fueled an evolution in the debate about
global warming that today challenges the world's political
leaders--and the public--to think about the weather their
grandchildren and great-grandchildren will experience.
While Manabe says he avoids political
wrangling, lest his research lose credibility, he has given "the
decision-makers," as he calls them, plenty to think about.
His work has brought him many honors,
including the 1993 Roger Revelle Medal from the American Geophysical
Union and the 1992 Asahi Glass Foundation Blue Planet Prize, a
$400,000 award that GFDL Director Jerry Mahlman once called "of
nearly obscene magnitude, but still modest relative to that received
by, say, a below-average major league ballplayer."
In 1993, when Manabe received the
Revelle Medal, Mahlman wrote: "I believe it is fair to say that the
state of our understanding of climate change would be perhaps a
decade behind today's level if he had chosen the medical profession
that his family appears to have preferred."
Grid mesh covered globe
At the start of Manabe's career, scientists were suspicious about
rising carbon dioxide levels, but the presence of a greenhouse
effect, first explored by the Swedish scientist Arrhenius at the turn
of the century, had not gained acceptance.
Starting with a simple one-dimensional
model of the atmosphere, Manabe and his colleagues progressed to
three dimensions, adding as many physical processes as the electronic
computer would permit at each stage.
They "covered the globe with a grid
mesh, computing temperature, wind and moisture at several thousand
grid points," Manabe said. "I set out to try to see the responses of
the systems to greenhouse gases, using the classical laws of physics.
I was very lucky that computer technology developed along the same
timetable."
Manabe's models evaluated the effects
of convective as well as radiative heat transfer between the earth's
surface and the troposphere, assessing the influence of carbon
dioxide, water and ozone on the climate. A 1967 paper with Richard
Wetherald of GFDL, published in the Journal of Atmospheric
Sciences, predicted how increased carbon dioxide levels due to
fossil fuel use could warm the earth.
Manabe's 1969 partnership with Kirk
Bryan, then a visiting senior research scientist and now retired from
GFDL, produced the world's first coupled atmosphere-ocean model. This
paved the way for their pioneering study of the role of oceans, which
they called "a giant heat sink," in delaying the pace of global
warming.
Up to 16 degrees in 500 years
Over time, scientists began to take seriously what Manabe's models
were telling them about increased levels of carbon dioxide in the
atmosphere. Talk of the greenhouse effect gradually moved out of the
labs and into the public arena, with the debate shifting to whether
humans are responsible for global warming trends of the 20th
century.
To Manabe, debating exactly how much
the earth will warm in the next 20 years misses the point. "We can
argue endlessly about that," he said. What's more important, he
feels, is that "If you keep burning fossil fuels and cutting tropical
rain forests, it will not be surprising if the concentration of
carbon dioxide quadruples. In several centuries, this could cause
warming that is almost as great as the difference between the period
of Jurassic Park and the present planet, with great
consequences for ecosystems and for life."
Manabe's model shows that surface
temperature over North America will warm between nine and 16 degrees
Fahrenheit in the next 300 to 500 years. He says that while his model
is "more sensitive" than those developed by other scientists, the
bottom line is the same: the earth is warming, and climate changes
will follow.
As their early work gained acceptance,
Manabe's group turned to other topics, looking both to the future and
to the past. Their studies of the past ice age have enabled them to
evaluate the sensitivity of their model against geological records.
Work on the relationship between atmospheric change and soil
saturation has led to the prediction that soils may become
increasingly dry in the summer.
More recently, the Climate Dynamics
Group has examined the "conveyor belt" that carries warm saline
surface water towards the North Atlantic ocean, making the climate of
Western Europe warmer. A large increase in precipitation in the
Arctic Ocean and surrounding regions, which is associated with global
warming, could cause this belt to slow down markedly, moderating its
warming effect in Western Europe.
Manabe's successor as head of the group
will be Isaac Held, senior scientist at GFDL and lecturer with rank
of professor in Geosciences and Atmsopheric and Oceanic Sciences.
More enthusiasm than alarm
For someone who has made dire predictions about the future of the
planet, Manabe discusses his findings with more enthusiasm than
alarm. His avoidance of the political debate he helped create does
not mean that Manabe lacks an interest in how it will unfold. While
ozone depletion is bad for all, he said, global warming "will likely
produce some winners as well as losers. Canada and Siberia may have
milder winters."
He predicts that using models to
generate increasingly precise data for specific regions will only
complicate matters.
"Our other alternatives are to adapt or
to find an alternative fuel source," he said. "Fusion may yet be the
answer. Molecular biologists may tell us how to adapt our
agriculture."
For now, Manabe will help other
scientists ponder the unanswered questions. He has accepted an
administrative post at a new climate study institute in Tokyo, while
retaining a relationship with Princeton. "I'll see how it goes," he
said with a smile. "If I'm not helping them, then I will reevaluate."
1013-greenh.html