Dr. Timothy A. Cohn, U.S. Geological Survey statistical hydrologist and expert on flood risks, water quality, and hydrologic trends, died at his home in Reston, surrounded by his loved ones, on Feb. 20, 2017, a few days short of his 60th birthday.
During his 30 years with the USGS, Cohn developed innovative tools to help scientists, engineers, and policymakers better understand water quality and floods in a manner that informs and protects Americans. His tools and concepts are used by federal agencies and are incorporated in software used worldwide. Cohn co-authored groundbreaking articles about the difficulty of discerning true trends in temperature, precipitation, and water quality data and avoiding false "detections" of trends in data subject to natural variation. He focused on climate and natural hazard issues and demanded rigor in analyzing climate change impacts. Cohn also had a major impact on how U.S. water quality scientists estimate pollutant loading to water bodies like the Chesapeake Bay.
Cohn inspired colleagues to identify scientific endeavors requiring the unique perspectives and capabilities of the USGS and mentored others to uphold high scientific standards. For his exceptional contributions as a civil servant, in April 2016 Cohn was granted the Department of the Interior’s highest honor, the Distinguished Service Award.
During his career Cohn served as the USGS Science Advisor for Hazards, was president of the American Geophysical Union (AGU) focus group on Societal Impacts and Policy Sciences, and served as an AGU Congressional Science Fellow in the office of U.S. Sen. Bill Bradley (as well as on Bradley’s presidential campaign). He also served on the Board of Governors and Executive Committee of the American Institute of Physics, the National Academy of Science Disasters Roundtable Steering Committee, and as an associate editor of Water Resources Research. Prior to his hydrology career, Cohn worked at the Brookings Institution as a research assistant to the Director of Economic Studies.
Cohn was born in Boston, Mass. on Feb. 26, 1957, son of Alfred B. Cohn and Barbara P. Norfleet. He grew up in Cambridge, attending the Shady Hill School and the Commonwealth School. He dropped out of high school to go to Colombia and work on Ingetec’s Chivor Hydroelectric Project, kindling a lifelong love of science and water. He then earned a BA in Mathematics from Swarthmore College, and an MS and Ph.D. in Water Resource Systems Engineering from Cornell University.
Cohn lived in Reston for over 30 years, where he raised his two children with his first wife Sarah Gerould. He was active in his community, serving on the board of the Reston Association, and as president of Reston Runners. He was an avid runner, completing countless shorter races and over 30 marathons including New York and Boston several times, many ultramarathons including the Vermont 100 miler, JFK 50 miler, Stone Mill 50 miler, and seven 50K’s. Since his cancer diagnosis Cohn competed with and coached for the American Cancer Society DetermiNation team — a cause which combined his love of running and desire to support others fighting cancer.
The cause of death was mantle cell lymphoma, which he battled for three years. As a scientist, Cohn was fascinated by advances in cancer treatment and participated in several clinical trials, including CAR-T cell immunotherapy. He hoped his participation in research would further scientific advances to benefit others, and is especially grateful to the entire team at Memorial Sloan Kettering for their expert and loving treatment.
Cohn is survived by his wife Sarah S. Humphrey, children Alexander Cohn and Hannah Cohn, mother Barbara P. Norfleet, brothers Frederick Cohn and Stephen Cohn, nephews Andrew Cohn, Chase Cohn, Dylan Cohn and niece Caitlin Cohn. The family requests that donations be directed to the American Cancer Society DetermiNation Team or Memorial Sloan Kettering Cancer Center.