Ralph Keeling

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Ralph Franklin Keeling (born 1957) is a professor at the Scripps Institution of Oceanography. He is the principal investigator for the Atmospheric Oxygen Research Group at Scripps and the director of the Scripps CO2 Program, the measurement effort behind the Keeling Curve started by his father, Charles David Keeling, in 1958.

Keeling grew up in Del Mar, California. He earned a B.S. in physics from Yale University in 1979 and a Ph.D. in applied physics from Harvard University in 1988. For his Ph.D. research, he developed a new method to measure atmospheric oxygen very precisely.

During his Ph.D., Keeling built his first scientific instrument, a light-gauging interferometer for measuring atmospheric oxygen. By October 25, 1986, he had a working prototype—a seven-foot-tall stainless steel box with a glass front. Light passes through air samples, and tiny changes in how fast light travels at different wavelengths reveal the air’s oxygen content with extraordinary precision (down to a few molecules per million).

Keeling’s Interferometric Oxygen Analyzer enabled detailed studies of atmospheric composition, the global carbon cycle, ocean biogeochemistry, paleoclimate, and climate change. He has collected data since 1989, contributing to key discoveries about the carbon cycle. His findings show that atmospheric oxygen is slowly decreasing, in a pattern related to the rise of CO2, though the decrease is not as fast as CO2 increases would predict.

A landmark 1996 study showed that land and ocean carbon sinks could be compared by examining the partial pressures of oxygen and CO2 in the atmosphere. Keeling’s data support the view that land habitats—plants and soils—are a major carbon sink, and that vegetation is taking up CO2 at a higher rate now than in the past. While deforestation and permafrost thaw release CO2, plants still absorb more CO2, helping to slow the rise in atmospheric CO2.

Beyond atmospheric oxygen, Keeling studies ocean warming, the stratification of the upper ocean, and ocean deoxygenation. Ocean models predict lower oxygen levels in the future, and notable drops have been observed in the North Pacific and tropical oceans over the last fifty years. He has also worked with Britton Stephens on Antarctic ice and glacial CO2, modeling CO2 during glacial and interglacial periods and exploring how ocean processes and Antarctic ice affect climate stability. He investigates thermohaline circulation and Southern Ocean currents to understand warming patterns.

Keeling also monitors local emissions around Los Angeles, including methane, and advocates for ongoing measurement of atmospheric gases and continued ocean monitoring. He emphasizes the importance of sustained funding to ensure the Keeling Curve and related scientific measurements continue.

Keeling has received several honors, including the Rosenstiel Award in 1992, a H. Burr Steinbach Visiting Scholar appointment at Woods Hole Oceanographic Institution in 1998, and the Humboldt Research Award in 2009 for his career achievements.