Citation for Gretchen Keppel-Aleks

Gretchen Keppel-Aleks, winner of AGU’s 2019 Global Environmental Change Early Career Award
Gretchen Keppel-Aleks

Dr. Keppel-Aleks is a rising leader in the carbon cycle community. Her research uniquely combines observational and modeling tools to increase understanding of the effects of climate variability on the carbon cycle. She has made notable contributions to our understanding of the role of the terrestrial land sink in a very short period of time and has linked a range of disciplines that represent the Global Environmental Change community.

To provide constraints from atmosphere and space-based observations, Dr. Keppel-Aleks has integrated remote sensing and ground-based observations to understand the flux of carbon from the terrestrial biosphere, including remote sensing data sets (such as NASA’s Orbiting Carbon Observatory (OCO-2)) and solar-induced chlorophyll fluorescence (SIF). In addition, Keppel-Aleks is part of a team to develop and deploy tower-based spectrometer systems to connect satellite-derived SIF and ecosystem models. Her research combines a suite of various and disparate observations and tools to improve our understanding of the terrestrial carbon sink. Further, Keppel-Aleks has linked this observational framework with that of the Earth system modeling community to improve our understanding of climate-driven variations in the global carbon cycle, using modeling tools such as the Community Earth System model.

Dr. Keppel-Aleks has already taken on several leadership positions in the field, including her participation on the OCO-2 science team, as a coauthor on the U.S. State of the Carbon Cycle Report (SOCCR-2), as a cochair for the Biogeochemistry Working Group for the National Center for Atmospheric Research Community Earth System model, and as a member of the Department of Energy’s International Land Model Benchmarking (ILAMB) team. Her nominators also cite her excellent mentoring of students in the community, and I have seen this firsthand at Michigan. Dr. Keppel-Aleks has developed a diverse group and provides the support to produce excellent science in her research team.

Dr. Keppel-Aleks is an outstanding young scientist who has developed a deep and broad approach to address one of the greatest environmental conundrums of this generation.

—Allison Steiner, University of Michigan, Ann Arbor


Thank you, Allison, for your kind words. It is humbling to have been nominated by a colleague who inspires me with her interdisciplinary research approach and with her commitment to forging a more equitable and inclusive scientific community. Both of these facets—interdisciplinarity and inclusivity—are necessary to confront the scientific and social challenges posed by climate change. The research that falls under the AGU Global Environmental Change section addresses the most pressing scientific questions faced by my generation, and it is an honor to receive this section award.

This award is a reminder of how privileged I am to engage in interesting and thought-provoking work each day. Much of the joy in doing science stems from the opportunity to collaborate with and learn from other scientists. This award reflects the outstanding mentorship from which I have benefited over the course of my career. I especially acknowledge senior scientists who have taught me how to think creatively and deeply about the Earth system and the tools we use to understand it, especially Scott Doney, Jim Randerson, Tapio Schneider, Geoffrey Toon, and Paul Wennberg. It has been a pleasure to have friends from my graduate and postdoctoral programs turn into collaborators and sounding boards, especially Dan Feldman, Tim Merlis, Brendan Rogers, Rebecca Washenfelder, and Debra Wunch. This award also affirms the efforts of the next generation of scientists whom I have been fortunate to teach and advise at the University of Michigan.

Finally, I want to thank my family, especially Aaron Wolf, for their support. On the days that I am not optimistic that human civilization is up to the challenge, the people I love keep me going.

—Gretchen Keppel-Aleks, University of Michigan, Ann Arbor

Citation for Abigail L. S. Swann

Abigail L. S. Swann, winner of AGU’s 2019 Global Environmental Change Early Career Award
Abigail L. S. Swann

Abigail L. S. Swann is being recognized with the Global Environmental Change Early Career Award for her innovative, interdisciplinary research coupling vegetation and the atmosphere. Dr. Swann has appointments in the Department of Atmospheric Sciences and the Department of Biology at the University of Washington. Her contributions lie within three overlapping areas: (1) She focuses on an obvious but amazingly overlooked set of processes: how vegetation change affects climate, both locally and elsewhere, subsequently affecting vegetation elsewhere—termed an “ecoclimate teleconnection.” (2) She possesses an extremely rare skill set enabling her to run Earth system models focusing on the atmosphere as well as running relevant linked ecological models. (3) She is rapidly, creatively demonstrating the relevance of ecoclimate teleconnections for a variety of vegetation response types, at a variety of spatial scales, and for a variety of applied problems.

Dr. Swann evaluated the consequences of afforestation (adding forests) to Northern Hemisphere grasslands, a commonly discussed carbon sequestration strategy, and showed that such vegetation change could alter the position of the Intertropical Convergence Zone. Dr. Swann also focused on the converse of regional-scale afforestation—regional-scale loss of tree cover from die-off or deforestation. Her simulations reveal important cross-hemisphere impacts of tree loss from western North America or the Amazon Basin.

The potential importance of ecoclimate teleconnections is profound. On the basis of the Paris Agreement, there is now an attempt to move toward globally coordinated carbon management. Dr. Swann’s work reveals how forest changes in one continent (e.g., either increasing or decreasing forest area) could affect another. Consequently, carbon gains in one area could have a negative impact on the productivity and associated carbon dynamics in another. This has profound implications for carbon management.

Abby is making enormous contributions to science, and I am extremely privileged to have had opportunities to collaborate with her.

—David D. Breshears, University of Arizona, Tucson


I am honored to receive the Global Environmental Change Early Career Award. Thank you, Dave, for nominating me and for your kind words. Collaborating with you has been a productive, educational, and thoroughly enjoyable experience.

I am lucky to have had the opportunity to work with many people who have broadened my scientific and academic thinking and helped me to tackle problems at the boundaries between traditional academic disciplines. I am grateful for my colleagues and collaborators who have provided both formal and informal mentorship. Inez Fung has played the central role in teaching me how to do science and be a scientist, serving as a mentor since I was an undergraduate. Becky Alexander, Cecilia Bitz, Gordon Bonan, Dave Breshears, Emily Fischer, Charlie Koven, Jim Randerson, Scott Saleska, and LuAnne Thompson have all provided critical support in science and beyond. I am so appreciative to have had the opportunity to work with graduate students and postdocs Greg Quetin, Marlies Kovenock, Marysa Laguë, Elizabeth Garcia, Jennifer Hsiao, Claire Zarakas, and Greta Shum. My peer support group of women scientists at the University of Washington has been invaluable in helping me through the day-to-day challenges of research and academia. I also owe a huge debt of gratitude to my partner and our two children for their love and support.

Finally, I am happy to join Gretchen Keppel-Aleks in the 2019 cohort for this early-career award; however, I strongly believe that as a community we can and must do more to increase nominations of and awards to women and scientists from underrepresented groups for all honors, but especially for early-career awards. In failing to represent all members of our community in awards and honors, we perpetuate a history of unequal opportunities for success in our field.

—Abigail L. S. Swann, University of Washington, Seattle

Citation for Yangyang Xu

Yangyang Xu, winner of AGU’s 2019 Global Environmental Change Early Career Award
Yangyang Xu

Yangyang Xu’s research has provided vital insights into major issues related to both the science of climate change and the mitigation of climate change. While still a graduate student, Xu led and completed a multi-institutional study on hydrofluorocarbon (HFC) forcing and its mitigation potential for 21st-century projected trends. This had a major impact on U.S. policy toward eliminating HFCs in refrigeration and helped provide the scientific basis for the Kigali Amendment to the Montreal Protocol.

Xu was also one of the first to show that black carbon heating contributed as much as half of the observed large warming over the elevated regions of the Himalayan–Tibetan region. A series of model-based investigations by Xu and his students and collaborators have shown aerosols from industrial activities to be an important influence on changes observed in the past few decades. These studies consistently demonstrate a more significant impact than was previously suspected for changes in precipitation extremes, latitudinal temperature gradient, drought indices, and snow cover.

In view of his significant contributions to our understanding of the physical mechanisms of climate change, their impacts, and their implications for national and international climate policies, Yangyang Xu is a highly deserving recipient of the 2019 Global Environmental Change Early Career Award.

—V. Ramanathan, Scripps Institution of Oceanography, University of California, San Diego, La Jolla


I deeply appreciate Ram for the nomination and a few of my colleagues at Texas A&M University for starting the process. I benefited greatly from the kind support and inspiration since I started working with Ram 10 years ago at the Scripps Institution of Oceanography. Ram has supplied me a flexible environment in which to explore various research topics and, more important, led me to do society-relevant climate research, which has become my main aspiration today. Through Ram, I had the chance to work with researchers in a multidisciplinary setting and have learned so much from them, especially David Victor (School of Global Policy and Strategy, University of California, San Diego) and Durwood Zaelke (Institute for Governance and Sustainable Development).

My gratitude needs to be extended to many scientists at the National Center for Atmospheric Research, where I worked for several years as a visiting student, postdoc fellow, and project scientist. The too-long-to-complete list particularly includes Warren Washington, Jean-François Lamarque, Jerry Meehl, Aixue Hu, Claudia Tebaldi, Simone Tilmes, Mary Barth, and Rajesh Kumar. The career mentoring and research advice from them continue to drive my research forward.

Since moving to Texas A&M, I have received tremendous support from many colleagues in the department as well as at the university, especially Andy Dessler, Ping Yang, Jerry North, Ken Bowman, John Nielsen-Gammon, Sarah Brooks, R. Saravanan, and Bruce McCarl. It has been a very productive and enjoyable 3 years in Aggieland.

Last and most important, I thank my family, especially my wife, Xiaoshan Gao, for her continuous sacrifice to support my (flexible) work schedule.

I’m honored by this award from the AGU Global Environmental Change section, and it will provide encouragement to my future research. Further motivation comes from the grand challenge imposed by the unprecedented rate of global and environmental change, to which I plan to devote my career. I hope the younger generations, my pre-K son and newborn daughter included, can testify (in 2100?) that we tried our best.

—Yangyang Xu, Texas A&M University, College Station


(2020), Keppel-Aleks, Swann, and Xu receive 2019 Global Environmental Change Early Career Award, Eos, 101, Published on 03 April 2020.

Text © 2020. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.

Text © 2020. AGU. CC BY-NC-ND 3.0
Except where otherwise noted, images are subject to copyright. Any reuse without express permission from the copyright owner is prohibited.