Wallace Smith Broecker (1931-2019) Geochemist Who Transformed Understanding of the Climate System

COMMENT OBITUARY Wallace Smith Broecker (1931-2019) Geochemist who transformed understanding of the climate system.

t was Wallace Smith Broecker who coupled with changes in ocean circulation, at pointed out in the 1980s that massive the surface and deep down. The climate sys- changes in global climate can arise from tem, Broecker noted in 1998, is like “an angry Imodest changes in ocean circulation. After beast and we are poking it with sticks” as we all, the oceans contain roughly 50 times pour greenhouse gases into the atmosphere. more carbon than does the atmosphere, and On 8 August 1975, Broecker published a are responsible for nearly half of global heat paper in Science entitled ‘Climate change: transport towards the poles. Are we on the brink of a pronounced global With monumental intellect and unbridled warming?’ (W. S. Broecker Science 189, curiosity, Broecker defined much of today’s 460–463; 1975). It was the first scientific use understanding of the climate system. His of ‘global warming’, something he did not neat, elegant solutions to complex Earth- want to be remembered for. He later offered science problems — expressed in more than a reward to anyone who could find an earlier 500 publications and 17 books — reshaped usage. The paper was remarkably well timed, entire disciplines. however: global temperatures have risen His path-breaking career spanned nearly consistently above baseline values since 1976. seven decades, during which he defined the Despite a shower of awards and positions ocean’s role in global climate change and car- recognizing his leadership, Broecker led a

JEAN-LOUIS ATLAN/PARIS MATCH/GETTY ATLAN/PARIS JEAN-LOUIS bon cycling, and used palaeoclimatic records simple life: jeans and jumpers, a dented car to understand how climate changed in the and a small, spartan apartment near Colum- past and its implications for our collective ocean circulation in which surface waters cool bia University. He had dyslexia and avoided future. A wellspring of transformative ideas, and sink at high latitudes, forming cold, deep computers, instead pencilling his manuscripts Broecker inspired generations of researchers waters that ventilate the abyss. However, the on yellow pads of paper in neat, flowing cur- to think expansively about Earth. timescale of this process was unknown. Broe- sive script, often graphing by hand. “I under- Raised in a conservative Christian family cker demonstrated that Atlantic deep waters stand the data better this way,” he would say. in Oak Park, Illinois, Broecker left his under- were only one to two centuries old, providing Later in his career, he became an oracle whom graduate studies at Wheaton College (where crucial constraints on rates of ocean flows other scientists consulted about their most he pledged to eschew smoking, drinking, and chemical cycling. This discovery linked exciting discoveries and ideas. dancing and films) in his home state for an theory and observations, and showed that the In April 2002, US billionaire Gary Comer internship at Columbia University’s then- oceans were much more dynamic than pre- contacted Broecker to ask why he had been Lamont Geological Observatory (now the viously thought, a finding crucial for under- able to sail his yacht, Turmoil, through Can- Lamont–Doherty Earth Observatory) in Pali- standing climate change — past and future. ada’s usually ice-blocked Northwest Passage. sades, New York, in 1952. He stayed for the These initial ocean radiocarbon profiles They quickly developed a close friendship. rest of his 67-year career, calling it his ‘Garden inspired Broecker to co-lead the first global After enjoying a campfire picnic with scien- of Eden’. During his undergraduate studies, ocean-sampling programme, the Geochemi- tists and students — a Lamont tradition — he met Grace Carder; they were married for cal Ocean Sections Study (GEOSECS), in the Comer turned to Broecker and said, “How 55 years, until her death in 2007. In 2009, 1970s. For decades, these data were used to can I help?” Comer went on to invest more Broecker married long-time close friend and answer fundamental questions about the 3D than US$25 million in accelerating climate technician Elizabeth Clark, who shared his flow and chemical processes in the oceans. research, training scores of early-career sci- love for science, puzzles and adventure. Generations of marine geochemists were entists and building a new geochemistry labo- With his warm, direct US Midwestern trained using Broecker’s GEOSECS-inspired ratory at Lamont. sensibility, wry smile and penetrating gaze, book, Tracers in the Sea (1982), complete with Wally, as he was always known, changed he was famously supportive of early-career “superproblems” designed to stump even the how we think about the climate system. His scientists who shared his appetite for hard cleverest students. work invited deep, cross-disciplinary inter- problems. He was equally famous for his The prospect of abrupt climate change was rogation of nature’s workings. Understanding impatience and explosive temper when it one of Broecker’s most transformative ideas. the stakes early in his career, Wally held him- came to sloppy science. And he was an epic In 1970, Broecker and Columbia graduate self and the Earth-science community to high prankster. When his good friend and col- student Jan van Donk published a study of standards. His legacy challenges us to acceler- league George Kukla hosted a distinguished ocean sediment cores that revealed for the ate our understanding of how our planet is panel of Chinese scientists to bolster the first time the tempo of glacial–interglacial changing, and what it means for humanity. ■ countries’ relations, Kukla and his visitors cycles: large ice sheets take tens of thousands settled into his car to go to dinner, only to of years to grow, but melt rapidly. The dis- Peter de Menocal is dean of science and a discover that Broecker had jacked it up onto covery launched decades of research into the professor of Earth and environmental science cinder blocks. cause of this nonlinear behaviour. Current at Columbia University in New York City. He His doctoral dissertation pioneered work shows that the climate changes asso- also found scientific sanctuary at Lamont, environmental applications of radiocarbon ciated with these transitions were indeed working with Wally over 30 years as a measurements. In the 1950s, physical ocean- large (15 °C of warming near the poles), fast student, colleague and friend. ographers were formulating a theory of global (taking just a few decades) and intimately e-mail: [email protected]