P. C. D. “Chris” Milly’s name is the first that comes to mind when considering problems at the intersection of climate science and hydrology. His exceptional impact is based on key publications that have influenced the field in ways most of us can only hope for. Much of his work addresses the scientific underpinnings of how and why surface hydrology is changing.

In a 2002 Nature paper, Chris showed that the spatial pattern of changes in 20th century flood frequencies reconstructed from climate models matched observed changes in very large river basins. Three years later, another Nature paper showed that climate models were able to reproduce multidecadal streamflow changes in major river basins on five continents. Until those papers were published, the prevailing view was that land process representations in climate models were far too crude to reproduce historic variations in hydrological processes.

Chris’s work also addressed a recurrent problem in climate change impact analysis: transferring results from coupled, but coarse-scale, global models to watersheds that they cannot resolve. In his 2001 Earth Interactions paper, he and co-author Dunne showed that the approaches most commonly used tend to amplify the climate change signal, mostly through overestimation of the temperature sensitivity of potential evapotranspiration. They revisited this topic in Nature Climate Change in 2016, highlighting consequences of this overestimation and providing an alternative methodology.

A recent (2020) Science paper is a seminal contribution to understanding the sensitivity of the discharge of the lifeblood of the U.S. Southwest, the Colorado River, to climate warming. The paper demonstrates that the ongoing downward trend in the river’s discharge is largely due to reduced albedo in the (previously) snow-covered parts of the basin, especially in late winter and early spring.

Finally, who in hydrology is not aware of Chris’s 2008 “Stationarity Is Dead” paper? As the title implies, the paper argues that in the era of hydrologic change, the fundamental underpinning of hydrologic planning and engineering design “is dead.” The impact of the paper has gone far beyond the hydrologic science community and is now embedded in the thinking of most water managers.

With the proliferation of journals, a lot of work is rushed out, broken into small pieces, and, ultimately, reduced to numerics. Chris’s approach is exactly the opposite. Everything he writes is based on exceedingly careful and thorough analysis. Both his research and the way he pursues it set an example for us all.

—Dennis P. Lettenmaier
University of California, Los Angeles
Los Angeles, California

—Kirsten Findell
NOAA Geophysical Fluid Dynamics Laboratory
Princeton, New Jersey

P. C. D. “Chris” Milly received the 2013 Hydrologic Sciences Award at the 2013 AGU Fall Meeting, held 9–13 December in San Francisco, Calif. The award is for outstanding contributions to the science of hydrology.  

It is with great pleasure that I introduce to you the 2013 Hydrological Sciences Award winner, Dr. Chris Milly. Chris is being honored “for fundamental contributions to our understanding of the connections between land surface processes and hydroclimatic variability.” Through Chris’s work, the world has a better understanding of how the Earth’s energy and water cycles interact at the large scale to determine hydrological quantities, such as streamflow, of fundamental interest to society. He is eminently deserving of this award.

After he earned his Ph.D. at the Massachusetts Institute of Technology (MIT) under Peter Eagleson, Chris moved to Princeton, where he established himself, as a U.S. Geological Survey (USGS) employee, as the resident hydrologist at the Geophysical Fluid Dynamics Laboratory (GFDL). There he contributes to GFDL’s overall scientific productivity by leading the development of the GFDL land model. Of course, while there, he also performs his own basic and vital hydroclimatic research. Chris’s recent work on climate stationarity in water resources management planning has challenged established paradigms—appropriately so—and his work on runoff in a changing climate garnered him media attention and even a presentation to Congress. His research papers indeed address a wide range of topics, more than I can outline here. Let me just say that he has a wonderful way of looking at problems: Use simpler models first to understand the mechanisms behind a physical phenomenon and only then add complexity to the models to fine-tune the understanding. While the appropriateness and overall elegance of this approach is lost on many scientists, with Chris, it is second nature.

On a personal note, I can say sincerely that Chris, by example, has strongly influenced my own approach to tackling scientific problems. I can only assume he’s had a similar impact on others.

Please join me now in congratulating P. Christopher D. Milly, the 2013 recipient of AGU’s Hydrologic Sciences Award.

—RANDAL D. KOSTER, NASA, Greenbelt, Md.

Thanks so much, Randy, for your generous comments! I accept this award on behalf of all the people I’ve had the plain dumb luck to fall in with over the last 40 years. I was lucky to be raised in a family that valued education and that even knew something about mass transfer at the soil-atmosphere interface. I was lucky to study under two great water-resource faculties, at Princeton and MIT, and to have Pete Eagleson as my mentor. I was lucky to be given a shot at a career in academia at Princeton. And, quite honestly, I was lucky that the university somehow saw I was not thriving there and encouraged me to explore other options. At that point, I also was lucky that I had spent a couple undergraduate summers working for John Bredehoeft at USGS and that Roger Wolff had subsequently kept the USGS in touch with me because that set the stage for what was next. As luck would have it, Marshall Moss at USGS and Jerry Mahlman at NOAA’s GFDL had the vision to write a memorandum of understanding between their organizations, under which a USGS hydrologist would be stationed at GFDL to work on hydrology in climate models. Luckily, I was in the proverbial right place at the right time, and both institutions took a long-term risk on me. I was lucky to receive the support of Suki Manabe when I arrived at GFDL, and I was very lucky to hire Krista Dunne to support all my research efforts ever since. I could also tell many lucky tales of coauthors and colleague reviewers, but my time is up. I was very moved to learn of this award. My sincere thanks goes to my nominators, to the Hydrologic Sciences Award Committee, and to my professional family—the AGU Hydrology section. Thank you all! —P. C. D. “CHRIS” MILLY, U.S. Geological Survey, Princeton, N.J.