Daniel P. Schrag

2001 James B. Macelwane Medal Winner

Harvard University

Daniel P. Schrag received the Macelwane Medal at the 2001 Fall Meeting Honors Ceremony on 12 December, in San Francisco, California. The medal is given for significant contributions to the geophysical sciences by young scientists of outstanding ability.


“My perception of Dan’s intellectual character leads me to start with his personal Precambrian. Dan’s education began at the Columbia Greenhouse Nursery School and Manhattan’s West Side Montessori School. From third grade onward he attended the schools operated by the Ethical Culture Society, a bastion of progressivism founded in 1878 by Felix Adler. The high school is the Fieldston School, where the physics laboratory is named after one of the alumni, J. Robert Oppenheimer.

“He was first listed as an author on a scientific paper during his sophomore year in high school, and during his senior year he was a national finalist in the Westinghouse Science Talent Search. That early work dealt with cellular immunochemistry. Earl Zimmerman, in whose lab Dan worked at the Columbia University College of Physicians and Surgeons, had given Dan responsibility for a small portion of a large project. It turned out to be more complicated than expected, but Dan was not inclined to give up. Moreover, the lab ran democratically and there was a great deal of interaction. Dan spoke up, worked hard, and, in spite of his youth, progressed from nuisance to productive collaborator to stimulating friend. A pattern was thus established.

“That privileged education worked, to say the least. It yielded a perpetually young man for whom thinking and science are fun. Influences from those of us who came later have been collegial rather than didactic. Dan enjoys nothing more than a discussion of, or, better, a debate about, ideas. This usually begins, and continues, with a challenging of assumptions. He’s not defensive and doesn’t mind being wrong. You’ll feel better about the conversation if you don’t mind being wrong either. Dan makes large leaps in thinking and catalyzes them in others.

“As an undergraduate at Yale, Dan was hooked on geology when Danny Rye told a class that people made progress in understanding the Earth if they were willing to ‘think outrageously.’ He completed majors in both geology and geophysics and political science. His senior theses dealt with a problem in economic geology and with changing interpretations of the politics of Robin Hood. He hoped to join the Congressional staff, but Danny and Brian Skinner encouraged him to try graduate studies. Dan chose Berkeley. There, he found a stimulating and challenging mentor in Don DePaolo.

“In his work, Dan combines a mastery of observational and analytical technology with a deep and insightful understanding of major problems in the Earth sciences. This duality appears first in his dissertation, which dealt with diagenetic effects on oxygen isotopes in marine carbonates and related effects on pore waters. With advice from Frank Richter, Dan modeled the relevant processes and ultimately reconstructed the abundance of oxygen-18 in seawater at the Last Glacial Maximum. The resulting dissection of temperature and ice-volume signals showed that earlier estimates of ocean temperatures had been much too warm and provided new mass budgets for the Laurentide and Fennoscandian ice sheets.

“Dan accepted an assistant professorship at Princeton and, with his coworkers, produced highly resolved records of seasonal variations in the abundance of radiocarbon in surface waters of the tropical Pacific. In work with Mark Cane and his students, Dan showed that these unexpectedly large and previously unrecognized signals could be cleanly interpreted in terms of changes in the circulation of surface waters.

“Moving to Harvard 3 years later, Dan quickly joined forces with Paul Hoffman to study the enigmatic carbon isotopic variations that accompany the geologic evidence for widespread, sea level glaciation at tropical latitudes during the late Proterozoic (Joe Kirschvink’s ‘Snowball Earth’). Mass balance required that nearly all carbon added to the sedimentary inventory during some time intervals be in the form of carbonate rather than organic material. Eliminating the impossible, an unproductive ocean on a planet with wide temperature contrasts, Dan happily explored the outrageous. His suggestion that the cap carbonates are the products of a prompt oceanic titration of atmospheric carbon dioxide has been the key to an entirely new view of this crucial interval of Earth history.

“For these accomplishments, others that I do not have space to mention, and, most of all, for accomplishments that lie in the future, I am pleased to recognize Daniel Schrag as a 2001 Macelwane medalist.”

—JOHN M. HAYES, Woods Hole Oceanographic Institution, Mass.


“Thank you, John, for your kind words. It is claimed that Sir Isaac Newton once said, ‘If I have seen further it is by standing on the shoulders of giants.’ I think he was speaking of Galileo, who died in the same year that Newton was born.

“I don’t mean to make any comparison with Newton or with Galileo—but one of the wonderful things about receiving the Macelwane medal is that it gives me the opportunity to thank some of the people who have lent their shoulders to me in the last several years. Whatever contributions I have made, they have all been with the help and support of others. Some have been giants, some have been teachers, some have been students, most have been friends. The full list is far longer than what I can read to you here, but I will try now to mention a few. I know that it can be quite dull to sit here and listen to a long list of names, but it is important to me to say these names, so please bear with me.

“In my second year at Berkeley, I was a floundering graduate student, with little self-confidence, and little enthusiasm for geology or science in general. Don DePaolo had faith in me when few people did. He returned my confidence and rekindled my passion for science. Many of you are probably aware of Don’s brilliant mind, and his incredible scientific intuition, but I can attest as well to his patience, his kindness, and his great generosity. One of the great gifts that Don gave me was a trip the University of Chicago to meet Frank Richter. During that and several later trips I took to Chicago to work on modeling, Frank opened my eyes to the joys of discovery, and raised my expectations for what I should achieve. He was critical and supportive, and always approached science with curiosity and good humor. These two mentors, Don and Frank, together and separately, encouraged and inspired me. Most of all, they taught me how much pleasure one can get from working on a scientific problem, and I wish to thank them for that most of all.

“But Don and Frank have not been the only mentors who have guided me. Michael Moore, a graduate student with me at Berkeley, took me to Indonesia, introducing me to coral reefs, thoughts about El Niño, and a love for field work in remote places. John Hayes invited me to Indiana for a semester as a post-doc, and opened my mind to the possibilities of analytical geochemistry. Paul Koch and Francois Morel looked after me as new faculty at Princeton, and expanded my views of science with their broad intellects and deep curiosity. Mark Cane patiently taught me about the oceans and climate, among other things, and continues to be my most important sounding board for new ideas. Michael Bender has listened to my ideas, always offering insight and perspective. And Wally Broecker, encouraged, inspired, and critiqued me through the years, and remains a great influence on me as he is to many others.

“And there have been many others. First, there are my students and post-docs, Heather Stoll, Tom Guilderson, Keith Rodgers, Konrad Hughen, Jane Alexander, Katharina Billups, Pascale Poussart, Ros Rickaby, Sasha Van Dusen, and MaryLynn Musgrove, not including scores of undergraduates. Each one deserves specific thanks for their scientific contributions, for all they have taught me, and for their patience with me. Ethan Goddard has been my laboratory manager at Harvard, and contributes his kind and gentle spirit to everything that is done in my group.

“I thank my mentors at Yale: Danny Rye and Brian Skinner.

“At Berkeley, I was taught by an exceptional group of graduate students, Rick Murray, Don Snyder, Dave Montgomery, Jay Pulliam, Tom Johnson and several others. They provided the core of my education in geology, and the source of much fun and adventure.

“As a graduate student, I was new to paleoceanography, but intent on promoting some controversial and perhaps even threatening ideas. Among the young paleoceanographers, three people, Lowell Stott, Jim Zachos, and Howie Spero, made time for me. It might have been easier to brush aside a brash young student, but they were patient, and helped introduce me to a field I had little contact with at Berkeley.

“At Princeton, I had exceptional colleagues including Jorge Sarmiento, George Philander, Tony Dahlen, Guust Nolet, Carlos Martinez Del Rio, Dan Rubinstein, and others.

“And at Harvard, my colleagues have created for me an intellectual playground. Paul Hoffman has been a friend and teacher, and a companion on the continuing scientific exploration of the snowball Earth. And my daily interactions intersect with so many: Mike McElroy, Steve Wofsy, Brian Farrell, Jim Anderson, Andy Knoll, Missy Holbrook, Rick O’Connell, Jeremy Bloxham, John Shaw, John Holdren, Bill Clark, and recently Ann Pearson. Each one of you contributes to the excitement I feel when Max and I walk to work every day.

“As I hope you can tell, for me, science is a social process. By this, I don’t mean the social context for our science, the relationship between understanding the Earth and the fate of human society, although this has always been of great interest to me and a motivation for some of my work. What I mean is that doing science is a social process. Ideas are created and refined from conversations with others. Arguments are framed, assumptions are questioned, but all through time spent with colleagues and friends, and hopefully with respect and good humor. There are so many people to thank for this: Jeff Severinghaus, Gidon Eshel, Ralph Keeling, Gideon Henderson, Edouard Bard, Lou Derry, Jess Adkins, David Lea, Maria Zuber, John Grotzinger, Dianne Newman, Doug Erwin, Sam Bowring, Ed Boyle, Lee Kump, Gerry Ross, Jerry Mitrovica, Arjun Heimseth, Peter DeMenocal, Dave Battisti, Jean Lynch-Stieglitz, Lonnie Thompson, Paul Falkowski, Jerry McManus, Danny Sigman, Harry Elderfield, Sandy Tudhope, and so many more. It is these people that continue to make science so much fun. To return to Newton, let me simply say that by putting our shoulders together, we all see further. And enjoy the ride a lot more.

“Again, thank you for this great honor.”

—DANIEL P. SCHRAG, Department of Earth and Planetary Sciences, Harvard University, Cambridge, Mass.