Wallace S. Broecker, a geochemist who issued early warnings on global warming — a term he helped popularize in the 1970s — and later developed a sweeping, widely accepted model for how the oceans circulate heat and affect Earth’s climate, died Feb. 18 at a hospital in Manhattan. He was 87.
The cause was congestive heart failure, said his daughter Cynthia Kennedy.
Raised in an evangelical Christian family in suburban Chicago, he grew up in a home where modern geological thinking was dismissed and where Earth was believed to be only a few thousand years old. But he eventually abandoned that false view of the planet’s history and became a grim prophet of its future, serving as one of the first researchers to predict rising temperatures as a result of carbon dioxide emissions from the burning of fossil fuels.
Sometimes described as “the grandfather of climate science” and the “dean of climate scientists,” Dr. Broecker spent more than six decades as a student and professor at Columbia University, based at the school’s Lamont-Doherty Earth Observatory in Palisades, N.Y., some 15 miles north of Manhattan.
Although he was often credited with putting the term “global warming” into scientific circulation, through a 1975 research paper that featured those words in its title, Dr. Broecker was probably best known for his research on the chemistry, history and grand structure of Earth’s seas and oceans.
Far from a vast and relatively unchanging body of water, he found that the oceans formed a delicate system, highly susceptible to changes in climate. While water was long believed to circulate from the surface to the deep seas only over the course of thousands of years, Dr. Broecker’s research indicated that it flowed from one region to another remarkably quickly, as part of what he dubbed the “great ocean conveyor belt.”
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His theory, quantified and synthesized in the mid-1980s from decades of his and others’ research, effectively holds that warm, shallow water flows from the South Pacific into the Indian and then Atlantic oceans, where it cools and sinks upon meeting cold water from the Arctic. The cold water then travels back toward the Pacific, where it is heated and rises, as the cycle begins anew.
Using novel dating techniques and studying ice cores from Greenland, he found evidence of sudden changes in the ocean’s deep currents, which he traced to rising temperatures and linked to further shifts in Earth’s climate. As the currents changed, wind, temperature and storm patterns changed as well — sometimes in a matter of years, rather than centuries or millennia.
Calling the great ocean conveyor belt the “Achilles’ heel of the climate system,” Dr. Broecker estimated that were it not for the belt’s current course, average winter temperatures in Europe would drop by 20 degrees or more.
“There is surely a possibility that the ongoing buildup of greenhouse gases might trigger yet another of these ocean reorganizations, and thereby the associated atmospheric changes,” he told Newsday in 1997. “Were this to happen a century from now, at a time when we struggle to produce enough food to nourish the projected population of 12 billion to 18 billion, the consequences could be devastating.”
Long interested in climate change, Dr. Broecker had previously worked under climate researcher Roger Revelle, helping to prepare a 1965 report for President Lyndon B. Johnson that linked fossil fuel emissions to rising sea levels, the melting of the southern ice cap and freshwater acidification.
In a 1975 article, “Climatic Change: Are We on the Brink of a Pronounced Global Warming?,” Dr. Broecker theorized that a natural cooling trend would soon give way to a rise in global temperatures. The paper marked the first scientific use of the term “global warming,” according to an article by NASA historian Erik Conway; Princeton geoscientist Michael Oppenheimer said he once traced the term to climatologist J. Murray Mitchell.
In an email, Oppenheimer wrote that Dr. Broecker’s “greatest work was on using radioisotope dating to estimate the speed at which water circulates from surface to deep ocean, how the ocean disposes of atmospheric carbon dioxide, and to measure sea levels of the distant past from features of ancient coral reefs.
“This work opened doors to understanding three of the most important aspects of the climate change problem: ocean circulation (of which the conveyor belt is one aspect), the global carbon budget and the relation of warming to sea level rise.”
Dr. Broecker later testified at congressional hearings on climate change, calling carbon dioxide “the number one long-term environmental problem.” And he became something of a guru among climate scientists and the journalists who sought them out, known as much for the breadth of his knowledge as for a temper that was invariably described as “volcanic.”
“He has single-handedly pushed more understanding than probably anybody in our field,” Richard Alley, a geosciences professor at Pennsylvania State University, once told the alumni magazine Columbia College Today. “He is intellectually so huge in how the earth system works and what its history is that all of us are following Wally in some way or another.”
Wallace Smith Broecker was born in Chicago on Nov. 29, 1931, and raised in nearby Oak Park, Ill. His father ran a gas station, and his mother was a homemaker.
Dr. Broecker initially studied at Wheaton College, a Christian school in Illinois. He was contemplating a career as an actuary when a classmate, Paul W. Gast (later the chief moon rocks scientist at NASA), encouraged him to apply for a summer internship at what was then Lamont Geological Observatory.
The internship proved transformative. Working under J. Laurence Kulp, a geochemist and Wheaton graduate, Dr. Broecker used new methods of carbon dating to study samples that were tens of thousands of years old. At Kulp’s encouragement he transferred to Columbia for his senior year of college, receiving a bachelor’s degree in geology in 1953.
While some peers taunted Dr. Broecker for his religious background, dubbing him and other evangelical Christians the “theo-chemists,” he came to view the Lamont observatory as a sanctuary, describing it in a 2016 memoir as “my geochemical Garden of Eden.” He received a doctorate in geology in 1958 and joined the Columbia faculty one year later.
Dr. Broecker was dyslexic and said he never typed or used a computer, writing manuscripts for his many books and articles by hand. He was often far away from his office, traveling across the oceans in search of water samples, seafloor cores or foraminifera, tiny marine animals useful for tracking ancient climatic change.
In 1987, he shared the Vetlesen Prize, a leading earth science honor, with geochemist and oceanographer Harmon Craig. The two researchers, the selection panel said, had “done more to characterize the chemistry of the oceans and its exchange with the atmosphere and the solid earth than any other scientists anywhere.”
President Bill Clinton awarded him the National Medal of Science in 1996.
Dr. Broecker’s wife of 55 years, the former Grace Carder, died in 2007. He married Elizabeth Clark, one of his lab workers, in 2009. In addition to his wife, survivors include five children from his first marriage; two children from a separate relationship; two sisters; seven grandchildren; and seven great-grandchildren. A daughter from his first marriage predeceased him.
Dr. Broecker expressed skepticism that humanity would be able to wean itself from fossil fuels anytime soon, and backed proposals for devices such as a “scrubber” that would suck carbon dioxide out of the air so that it could be safely stored underground. Although such an invention seemed drawn from the pages of a science-fiction novel, drastic change was essential, he said.
As Dr. Broecker put it, “The climate system is an angry beast, and we are poking it with sticks.”
Correction: Relying on information from Columbia University and Dr. Broecker’s family, a previous version of this obituary gave an incomplete list of survivors, omitting his two children from a relationship. The story has been updated.
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