Steven C. Wofsy

2012 Roger Revelle Medal Winner



Steven C. Wofsy was awarded the 2012 Roger Revelle Medal at the AGU Fall Meeting Honors Ceremony, held on 5 December 2012 in San Francisco, Calif. The medal is for “outstanding contributions in atmospheric sciences, atmosphere-ocean coupling, atmosphere-land coupling, biogeochemical cycles, climate, or related aspects of the Earth system.”



Steven C. Wofsy has made ground breaking contributions to atmospheric chemistry, biogeochemistry, and carbon cycle research.  A hallmark of his work is the way he uses observations and models to develop and test new concepts. If data are lacking, he builds an instrument to obtain the necessary measurements; if a conceptual or numerical model is lacking, he develops one.  Steve has spent his entire career at Harvard University.


Steve was ahead of the crowd in recognizing the role of bromine (BrO) in destroying stratospheric ozone in the 1970s and in elucidating the importance of the BrO + ClO cycle for formation of the Antarctic ozone hole in the 1980s.  He started one of the earliest laboratory programs to measure fluxes of N2O, which led to quantification of human sources of this greenhouse gas.   His group developed an aircraft instrument to measure CO2; their measurements showed how the trend and seasonal cycle of CO2 propagate into the stratosphere, and so quantified the “age” of air in the stratosphere.  Their data provide a critical constraint on stratospheric dynamics in chemistry-climate models.


The field campaigns Steve coled in the 1980s were the first exploratory missions to examine the role of natural ecosystems in the biogeochemistry of the major greenhouse gases. His aircraft measurements of CO2 and other species revealed the richness of interactions between remote and local emissions and led to improved inventories for CO, CH4, N2O, CFCs, and halocarbons. His group pioneered the use of surface and aircraft measurements to infer regional surface fluxes of CO2 and other gases. The overall data assimilation framework they developed has become the state-of-the-art for estimating the continental-scale budgets of these species. Steve conceived the HIPPO program to provide highly resolved aircraft profiles of pollutants from pole to pole, bridging the gap between surface and satellite data.


Steve’s group pioneered the long-term deployment of eddy covariance measurements for determination of CO2 and energy fluxes.  Year-to-year variations in these fluxes revealed the sensitivity of ecosystem functioning to climate perturbations.  Their long-term flux time series have challenged conventional ecological understanding of the controls of CO2 fluxes from boreal, temperate, and Amazon forests. Measurements from Harvard Forest, which started in 1990, show the net uptake of CO2 has doubled, even though this forest is of an age when models predicted it would be close to equilibrium.


Steve saw the potential for year-round flux observations and deserves much of the credit for opening this field.  He accelerated research by sharing the techniques his group developed, by championing open data sharing, by building and advocating programs such as the North America Carbon Program and AmeriFlux, and by providing a legacy of well-trained scientists.  He is a tireless and enthusiastic leader, a great teacher, and an inspiring mentor. His contributions have been recognized by the Macelwane Award, NASA’s Distinguished Service Medal, and, in 2011, by election to the National Academy of Sciences. It is fitting that he now receives the Revelle Medal.


Jennifer A. Logan, Harvard School of Engineering and Applied Sciences, Cambridge, Massachusetts



Modern views of the Earth’s climate, oceans and atmosphere, and appreciation of human impacts on these systems, are relatively new.  Less than a decade before I started my professional career, a small nucleus of pioneering scientists, including many previous recipients of the Revelle Medal, began to discern unexpected changes in atmospheric composition and to assess the implications for the global environment.  They initially did not imagine that global environmental changes would be observed in their lifetimes: The Earth system was thought to be too massive compared with human endeavors.


The stratosphere, and especially the ozone “hole,” gave the first irrefutable indication that humans could have major global impacts, with the chilling sidebar that these could occur without our notice.  Today we see accelerating increases in atmospheric CO2, astonishing retreats of floating ice and mountain glaciers, lengthening growing seasons, pollution of inland and coastal waters, and unsettling changes in ecosystems. Some of these large scale changes can be confidently attributed to human intervention; basic physics and chemistry tell us that mankind contributes significantly to all, with much more to come in the future.


Scientists would like to pursue understanding of these phenomena with the dedication, passion, open discussion, and objectivity of the previous generation, and then to effectively communicate the implications to the public. But our field is beset with distractions associated with loud public discourse that misses at least two key points: the global environment is very complex and nonlinear, and human activities challenge global systems on a scale hitherto unimagined. We ignore the risks at great peril to future generations.


It is an amazing honor to receive this Revelle Medal. Many, many people, too numerous to list,share this honor.  My career has been based on collaborations with a great number of iconoclastic scientists, both younger and older than I, who shared their ideas, knowledge, and enthusiasm to test and overthrow accepted paradigms. I mention a few of longest association: my mentor Michael McElroy, who introduced me and many others to the holistic view of Earth as a planet; colleagues who knew how to drill down to (and through!) the fundamentals: Jennifer Logan, Michael Prather, Yuk Yung, Dak Sze, Jim Anderson, Daniel Jacob, and Clarissa Spivakovsky.  Inez Fung’s 1983 paper simulating global CO2 begged to be tested, leading to long term eddy flux observations.  Collaborators who knew how to design sensors and field missions that could really test important ideas: Bob Harriss, the late Art Schmeltekopf, Bruce Daube, Bill Munger, and Christoph Gerbig. And nobody has had more support and understanding at home than I have from spouse Catherine and children Ray and Jonathan.


–Steven C. Wofsy, Harvard University, Cambridge, Massachusetts