Much of the modern understanding of climate change is underpinned by pioneering studies done at Columbia University’s Lamont-Doherty Earth Observatory. Starting in the 1950s and continuing today, researchers at sea, on land and in the lab have worked in disciplines including oceanography, atmospheric physics, magnetism, geochemistry, glacial geology, paleontology, tree-ring studies and more. Over five decades, they have shed light on how long- and short-term natural climate cycles work; the central role of atmospheric carbon dioxide; the hidden role of oceans: the possibility of extremely abrupt shifts; the potential effects on nature and on human societies; and, most recently, potential ways to address human-influenced climate change. Below: a timeline of some of the significant studies.
1956: A theory of ice ages Maurice Ewing and William Donn, Science Maurice “Doc” Ewing, one of the world’s most influential figures in oceanography and Lamont’s first director, teamed with geologist/meteorologist Donn to propose that ice ages are driven by self-perpetuating natural cycles of freezing and thawing of the Arctic Ocean. This paper and two followups were seized upon in popular literature of the time to suggest that a new ice age would arrive soon. They and others refined their ideas as more evidence came in, but this began the Lamont tradition of seeking the root causes of large-scale climate swings.
1960: Natural radiocarbon in the Atlantic Ocean Wallace Broecker et al., Journal of Geophysical Research Wallace Broecker—often called a grandfather of modern climate science—showed how isotopes of carbon produced by natural and human-driven processes could be used to trace the flow of ocean currents in a series of global-scale loops. It helped lead to an overarching model of a “Great Ocean Conveyor Belt” linked to climate, and understanding of how changes in currents may bring sudden, powerful shifts.
1966: Paleomagnetic study of Antarctic deep-sea cores Neil Opdyke et al., Science By systematically examining Antarctic seabed sediments, Opdyke and colleagues showed that periodic shifts in earth’s magnetic polarity could be used to accurately date deposits back beyond 2 million years—and thus climate shifts indicated by changes in dominant plankton species, and debris from melting glaciers. Previously, the limit was only 25,000 years. This set the stage for serious tests of theories of climate change in the distant past.
1973: Are we on the brink of a pronounced global warming? Wallace Broecker, Science Generally credited as the paper that coined the phrase “global warming.” At the time, the planet was emerging from a decades-long natural cooling cycle. Broecker postulated that it had been masking an ongoing warming effect caused by rising industrial carbon-dioxide emissions—a concept first raised in the early 1800s, but never proven. He predicted that once the cooling cycle bottomed out, global temperatures would rise swiftly. He was right.
1976: The surface of the ice-age Earth CLIMAP, Science CLIMAP, an international project in the 1970s-80s, reconstructed the world’s sea-surface temperatures, and thus overall climate, during the last glaciation. The main evidence was deep-sea cores—many taken by Lamont scientists and held in the Lamont Core Repository, the world’s largest collection of such samples. It was the first comprehensive look at earth’s temperature for a time markedly different from our own.
1976: Variations in earth’s orbit—pacemaker of ice ages James Hays, John Imbrie, Nicholas Shackleton, Science In the 1920s, Serb mathematician Milutin Milankovic proposed that earth’s ice ages coincide with cyclic changes in the eccentricity, axis orientation and wobble of the earth as it orbits the sun. This paper finally proved to most scientists’ satisfaction that Milankovic cycles are real. Lamont’s James Hays worked with two other giants of modern science: Brown University’s John Imbrie and Cambridge’s Nicholas Shackleton.
1978: The Marine oxygen isotope record in Pleistocene coral, Barbados, West Indies Richard G. Fairbanks et al., Quaternary Research Documented the magnitude and rapidity of sea level rises as ice sheets and glaciers melted during previous glaciations of the earth. Other Lamont researchers have followed this with many more studies up to the present, to quantify past changes in sea level—a key to understanding how current melting of ice may affect earth in the near future.
1986: Experimental Forecasts of El Niño Mark Cane, Stephen Zebiak et al., Nature El Niño is an irregular natural cyclic change in the temperature of the tropical Pacific Ocean that shifts rainfall patterns, and food yields, over much of the world every five to seven years. Until recently, its causes and timing remained little understood. Cane and Zebiak were the first to construct a model of its physics that successfully could predict shifts. This work introduced medium-term forecasts now used worldwide in planning for agriculture and emergency relief efforts.
1986: Inter-Ocean Exchange of Thermocline Water Arnold Gordon, Journal of Geophysical Research In conjunction with earlier oceanographic work, Gordon laid out how differences in the temperature and salt levels in different layers drive the exchange of water between oceans, and, ultimately, affect climate over vast distances. He and colleagues continue to work on questions of large-scale ocean circulation.
1989: The role of ocean-atmosphere reorganizations in glacial cycles Wallace Broecker and George Denton, Geochimica Cosmochimica Acta Explored the role of freshwater inflow into the northern North Atlantic, via melting ice, in governing the oceanic “conveyor belt,” and its possible association with disruptions of currents that could cause sudden, large-scale climate changes. Followed by many other papers including 1992’s Evidence for Massive Discharges of Icebergs into the North Atlantic Ocean During the Last Glacial Period (Gerard Bond et al., Nature).
1995: Temperature histories from tree rings and corals Edward Cook, Climate Dynamics Cook, now head of Lamont’s pioneering Tree Ring Lab, showed how tree rings dating back as far as 1,000 years correlated with both modern instrumental records and marine corals to show anomalous warming during the 20th century in many parts of the world. Working from places ranging from Tasmania and South America to Mongolia, North America and Scandinavia, lab scientists have since published many more papers on how tree rings illuminate regional and global climate histories. These include a 1989 reconstruction of temperatures across North America going back over 300 years by Gordon Jacoby and Rosanne D’Arrigo that shows the effects of global warming, and a monumental drought atlas of Asia, published in 2010.
1995: Plio-Pleistocene African climate Peter de Menocal, Science This connected the evolution of humans with a shift toward more arid conditions in the east African climate after 2.8 million years ago. The change resulted in the development of open savannahs where newly upright human hunters are thought to have adapted, and thrived. It was one of the early papers suggesting climate’s basic effects upon humans. Many scientists today continue investigations of the evolution-climate link.
2000: Climate change and the collapse of the Akkadian Empire: evidence from the deep-sea Heidi Cullen, Peter de Menocal et al. Geology The Akkadians, an early sophisticated civilization, ruled the Middle East until 4,200 years ago, when they suddenly collapsed. Heidi Cullen—later a well-known science author and TV figure—linked it with an abrupt 300-year drought, using layers of dust found in seabed deposits. This helped nourish an emerging awareness of how environmental change may affect societies. Later related Lamont papers include a 2010 study by tree-ring researchers exploring the collapse of southeast Asia’s Angkor culture in the 1400s, and other Asian societies, also apparently due to drought.
2002: Global sea-air CO2 flux based on climatological surface ocean pCO2, and seasonal biological and temperature effects Taro Takahashi et al., Deep-Sea Research Part II Based on some 940,000 measurements taken over four decades, Taro Takahashi and colleagues mapped for the first time on a global scale the exchange of the greenhouse gas carbon dioxide between the atmosphere and oceans—a flux that plays a key role regulating climate. This was followed by many other papers, including 2009’s Reconstruction of the history of anthropogenic CO2 concentrations in the ocean (Samar Khatiwala et al., Nature), which indicated that since 2000, the world’s oceans have begun losing their ability to absorb rising human emissions of carbon.
2004: “Long-Term Aridity Changes in the Western United States,” Edward Cook et al., Science The tree ring lab showed that a then ongoing drought in the U.S. Southwest paled in comparison to one about 1,000 years ago. The paper suggested that the region is extremely vulnerable to disastrous drying during periods of climate warming. An influential 2007 paper followed, led by climate modeler Richard Seager (Model Projections of an imminent transition to a more arid climate in southwestern North America,” Science), which suggests that the region will dry significantly in the 21st century, and that the transition to a long-term more arid climate may already be underway.
2008: In Situ Carbonation of Peridotite for CO2 Storage Peter Kelemen, Juerg Matter, Proceedings of the National Academy of Sciences With the recognition of the problems caused by rising carbon dioxide, Lamont scientists in several disciplines were among the first to work on possible ways to capture and store emissions. This paper documents efforts to use natural chemical reactions within rocks to “freeze” emissions into underground reservoirs. Projects by other researchers are looking into piping emissions into the seabed off the U.S. Northeast, or using rocks common on the U.S. mainland.
2011: Varying boreal forest response to Arctic environmental change at the Firth River, Alaska Laia Andreu-Hayles et al., Environmental Research Letters Showed that evergreen trees at the edge of Alaska’s tundra are growing faster in a warming climate—one of a rising tide of studies indicating how climate is changing ecosystems worldwide.
2011: Civil conflicts are associated with the global climate Solomon Hsiang et al., Nature In the first study of its kind, linked periodic increases in civil conflicts to the arrival of El Niño; the study found that the characteristic hotter, dryer weather doubled the risk of warfare across some 90 tropical countries, and accounted for a fifth of worldwide conflicts in the past 50 years. El Niño is a natural cycle, but there is evidence from studies done at Lamont and elsewhere that its effects could be intensified by rising global temperatures in the future.
2012: The geological record of ocean acidification Bärbel Hönisch et al., Science Showed that the world’s oceans are turning acidic at a rate unprecedented over at least the last 300 million years, apparently due to reactions with human emissions of CO2. This has grave implications for marine ecosystems, says lead author Bärbel Hönisch.