|Wallace Broecker, circa 2010 (Bruce Gilbert. Courtesy|
Lamont-Doherty Earth Observatory)
From Columbia University Earth Institute
Wallace Broecker, a geochemist who initiated key research into the history of earth’s climate and humans’ influence upon it, died Feb. 18 in New York. He was 87. The cause was congestive heart failure, said his family. His death was confirmed by Columbia University’s Lamont-Doherty Earth Observatory, where he spent a career that spanned nearly 67 years.
One of the first scientists to predict an imminent rise in earth’s temperature due to human output of carbon dioxide, Broecker was credited with introducing the phrase “global warming” into the scientific lexicon in the 1970s. Much of his work focused on the oceans. Among other things, his studies of marine chemistry helped lay out the map of global ocean circulation, and its powerful effects on climate. His studies also helped lay the basis for many other scientists’ work in a variety of fields. Not content to just do research, he made friends with and extended his influence to powerful figures in government and business.
Broecker—universally known as Wally—at first made an unlikely scientist. Born Nov. 29, 1931, the second of five children, he grew up in the Chicago suburb of Oak Park, Illinois. His father, also named Wallace, ran a gas station. His mother was the former Edith Smith. Both parents were evangelical Christians who rejected modern geologic theory for the literal Biblical interpretation that the earth is just a few thousand years old. They also forbade drinking, dancing and movies. Broecker attended Illinois’ fundamentalist Christian Wheaton College, then the recent alma mater of preacher Billy Graham. While still a student, he married the former Grace Carder, and spoke of becoming an insurance actuary.
Broecker got sidetracked after an older Wheaton student helped him arrange a summer 1952 lab internship at what was then called Lamont Geological Observatory, in Palisades, N.Y. The student was Paul Gast, who later went on to head NASA’s moon-rock program. At Lamont, Broecker worked with J. Laurence Kulp, a geochemist doing pioneering work on radiocarbon dating, a then revolutionary new method that allowed researchers to tell the ages of materials as far back as 40,000 years.
By his own account, Broecker had fun tinkering with the lab equipment, and he was excited by the newly wide-open chance to make discoveries about nature using carbon dating. He transferred to Columbia that fall and kept working with Kulp. The move suggested he had rejected at least some of his family’s religious beliefs; however, some other students made fun of his background, calling him a “theo-chemist.” While other students were sent on ocean research cruises, he was left off the list for his first eight years. Nevertheless, he earned a PhD. in geology in 1958 and stayed around, gradually rising to the first rank of prominence. In a 2016 memoir he called Lamont “my Garden of Eden.”
“My great joy in life comes in figuring something out,” he told The New York Times in 1998. “I figure something out about every six months or so, and I write about it and encourage research on it, and that’s the joy of my life.”
One of Broecker’s first achievements was a series of papers demolishing the stock idea that it took tens of thousands of years for water to circulate between shallow and deep regions of the world’s oceans. His analyses of carbon isotopes collected by Lamont ships from around the world showed that water could make the switch in just centuries—a discovery showed that the oceans are far more dynamic than previously thought. This in turn implied that the oceans could potentially affect the composition of the atmosphere, or vice-versa.
|Using chemical tracers and other data, Broecker laid out the |
picture of global ocean circulation, and its implications for climate.
(Courtesy Lamont-Doherty Earth Observatory)
Starting in 1960, Broecker sailed on many of the world’s oceans and seas. In addition to sampling water, he maintained instruments, helped winch seafloor sediment cores to the surface, and threw dynamite overboard to produce explosions whose echoes were read to chart the bottom. In the 1970s, he co-led a global program funded by the U.S. government to use a wide variety of trace metals, nutrients and isotopes of radioactive elements to map the circulation of the deep ocean, the exchange of gases with the atmosphere, and other marine processes. This collective work provided the underpinnings for virtually all later studies of marine chemistry, and the oceans’ relationship to climate. It was Broecker who provided a running commentary for a documentary film on the project while on a cruise from Tahiti to San Diego. He used related geochemical methods to study lake waters, sediments and rocks in Canada and the American West for clues about climates of the past, with a special interest in the comings and goings of ice ages.
Early on, Broecker became interested in how the oceans absorb carbon dioxide from the air, and what effects this might have on climate. The history and behavior of atmospheric carbon dioxide were poorly known when he started out, but by the early 1970s, other researchers had analyzed ice cores from the Greenland ice and shown that they could track levels of atmospheric CO2 through the distant past. Work by others suggested that higher CO2 levels could be correlated with periods of warming. And scientists had speculated since the 19th century that rising output of human-produced CO2 could potentially warm the planet; some of Broecker’s contemporaries, including Charles Keeling of the Scripps Institution of Oceanography, were already tracking CO2 levels in real time and considering the effects.
In August 1975, Broecker synthesized his and others’ related research in the journal Science in a piece called “Climatic Change: Are We on the Brink of a Pronounced Global Warming?” It was later said to be the first time the phrase was used in a scientific paper. In it, he argued that humans were changing the climate by emitting CO2; it just wasn’t evident yet, because the world was experiencing what he believed was a natural 40-year cooling cycle that was masking the effects. He predicted that the cycle would soon reverse, and then the manmade warming on top of that would become dramatically visible. It later turned out that he had misinterpreted some of the ice-core data, but had the overall picture right. Right on cue in 1976, temperatures started ascending, and have continued since then pretty much along the trajectory Broecker laid out.
|Receiving the National Medal of Science from President Bill Clinton,|
1996 (Courtesy Lamont-Doherty Earth Observatory)
And since the ocean has roughly 60 times as much CO2 as the atmosphere, it also move vast amounts of CO2 around and sequesters it.
“Global warming” was quickly adopted by the science world, including in the first large-scale report on the subject, published in 1979 by the U.S. National Academy of Sciences. Decades later, when some credited Broecker with coining the phrase, he shrugged it off as “dumb luck.” He warned that he would turn over in his grave if someone put “global warming” on his tombstone. He once offered $200 to any student who could find an earlier citation for the phrase. (One postgrad did find it in a 1958 editorial in the Hammond Times of Indiana. It apparently didn’t catch on at that time.)
Broecker and a handful of other scientists began briefing government leaders on climate change in the 1980s. He testified at the first congressional hearings dealing with the subject, led in 1984 by then Tennessee Representative Al Gore. Over succeeding years, as the science advanced, Gore and other politicians repeatedly met with and consulted Broecker to have him explain.
In the mid-1980s Broecker synthesized a grand picture of world ocean circulation, based on his and others’ studies. He dubbed it “The Great Ocean Conveyor.” In simplest terms, it is a vast river of warm, shallow water flowing from the south Pacific into the Indian Ocean, rounding Africa and then heading north through the Atlantic. Once it hits cold water from the Arctic, the water then cools and sinks near northern Europe. From there, it loops through the abyss back to the Pacific to warm, rise and begin the cycle again. The flow is so huge, Broecker asserted, that it must help regulate global climate by moving around vast amounts of heat from one place to another. This idea soon became general consensus.
Broecker then put forth the idea that the conveyor could suddenly switch on and off, leading to drastic climate shifts–not over millennia, as many had come to think, but perhaps just decades. He pointed to an apparently rapid cooling some 12,000 years ago that threw Europe and other regions into a temporary deep freeze. Paradoxically, he argued, the cause might have been a then-warming climate and the collapse of northern ice sheets, which introduced a pulse of freshwater that pushed back on the conveyor. He warned that “the uncontrolled experiment” of modern human-induced warming might bring similar rapid changes. He was fond of saying, “The climate system is an angry beast, and we are poking it with sticks.”Broecker was one of the few scientists I know of who could be universally known just from his first name. RIP, Wally.
Climatologists are still debating whether and how rapid climate swings might take place today. That notwithstanding, Broecker’s ideas were taken up and wildly exaggerated in the 2004 movie The Day After Tomorrow, which featured a climate-change-powered tsunami engulfing Manhattan and then freezing into an ice sheet–all in the same day. They were more credibly explained in possibly the only pop song about physical oceanography, “Uncle Wally’s Tale,” by the singer Tom Chapin. (Chapin was Broecker’s brother-in-law, married to Broecker’s younger sister, Bonnie.)