Steven J. Davis

University of California, Irvine

2018 James B. Macelwane Medal Winner

Steven J. Davis, Walter Immerzeel, Isaac Santos, Drew Turner, and Caroline C. Ummenhofer were awarded the 2018 James B. Macelwane Medal at the AGU Fall Meeting Honors Ceremony on 12 December 2018 in Washington, D. C. The medal is for “significant contributions to the geophysical sciences by an outstanding early career scientist.”


Davis’s research combines economic and geophysical approaches that are groundbreaking. He has carved a new field relating human systems, the carbon cycle, air pollution, and climate change, thus providing solutions for some of the most significant environmental challenges of the 21st century.

Davis developed the theory for tracking carbon dioxide (CO2) emissions that are embodied in all the goods and services traded internationally. Davis learned econometric methods and applied them in an analysis that was timely and salient: International climate negotiations were mired in the debate over whether developing countries should be required to reduce their CO2 emissions. By quantifying emissions that are effectively “outsourced” from developed countries, his work provides a rigorous scientific foundation that has informed ongoing policy discussions. By recognizing the interconnectedness and universally shared responsibility for these emissions, his work contributed to the success of the 2015 Paris Climate Conference, with the subsequent agreement creating a more level playing field for all nations.

Davis made another important breakthrough in tracking future global CO2 emissions from existing energy infrastructure. Even if we never build another power plant or car, assuming that existing infrastructure continues to operate for its expected lifetime causes a certain amount of emissions to be locked in. This new approach has focused the policy community on the implications of near-term plans by many developing countries to expand the number of fossil fuel–emitting power plants, given that normal operating lifetimes for these facilities can be 30–40 years. In more recent work, Davis and his colleagues have quantified the health impacts (and human mortality) associated with global trade flows, leveraging his earlier breakthrough linking CO2 emissions and trade.

Davis’s unique background combines a legal education, a dissertation on isotope geochemistry, work with nongovernmental agencies on life cycle assessment, and a postdoctoral analysis of energy systems. This gives Davis a diverse set of research methods. As a colleague in the Earth System Science Department at the University of California, Irvine, we truly value Davis’s vision and comradery.

Steve represents a new 21st century generation of geophysicists. We are thrilled that he is this year’s Macelwane Medal winner.

—James Randerson and Ellen Druffel, University of California, Irvine


I’m honored and humbled to accept the Macelwane Medal. Thank you, Jim and Ellen, for nominating me and for your generous citation. I’m fortunate to have you both as role models and colleagues, and I can only hope to distinguish the award as you both have.

I’m also grateful to AGU and the medal committee for selecting me among so many deserving young scientists. In doing so, they highlight the breadth of modern geophysical research in a way that I hope encourages and emboldens others to color outside the lines.

As Jim and Ellen mention, my path has been winding, and though they portray my varied background in a flattering light, it was less strategic building of experience than following my interests and trusting they would lead me to somewhere I wanted to be. Luckily, I happened into some terrific mentors who were audacious enough to give me a chance. Without them, I would never have become the scientist I am today.

Still a corporate lawyer, I walked into Page Chamberlain’s Stanford office one afternoon and did my best to convince him that I wanted to be a geologist. In retrospect, I was incredibly naïve, and I can’t for the life of me understand what he saw in me that day, but he took me on as a graduate student and over the next 4 years transformed me from an attorney with a philosophy degree into an isotope geochemist.

Ken Caldeira enabled yet another leap, hiring me as a postdoc at the Carnegie Institution to work on CO2 embodied in international trade on the basis of a fun lunchtime conversation we had—again despite my knowing almost nothing about the subject. What was supposed to be a few months turned into nearly 5 years in productive pursuit of the interesting and important.

Perhaps as important as the opportunities these men afforded me, they taught by example how to balance careful execution of science with bold hypotheses, how to resist common knowledge, to be more critical of yourself than you are of others, and that data are lifeless without a good story. These lessons were bolstered by other outstanding collaborators and mentors like Rob Socolow, Jen Burney, David Lobell, Glen Peters, Dabo Guan, Qiang Zhang, Rob Jackson, and Noah Diffenbaugh. My colleagues at the University of California, Irvine, have also been constant supporters of my work. I am indebted to them all. I hope that my mentorship can inspire and enable other students and postdocs as theirs has me.

Most of all, though, I am thankful for the love and unwavering support of my wife, Kristen; my parents; and my daughters. They have given me both the confidence to chase big ideas and the reason for the chase.

—Steven J. Davis, University of California, Irvine