Quantitative Hydrologic Storylines for Climate-changed Futures
Jeff Arnold, Senior Scientist and Lead Climate Scientist
U.S. Army Corps of Engineers.
Climate change narratives for water-resource applications must represent change signals contextualized by hydroclimatic process variability and uncertainty at multiple scales. Building probabilistic narratives of plausible change requires assessing uncertainties across GCM structure, internal climate variability, climate downscaling methods, and the set-up and parameterization of hydrologic models. Work in this linked model chain, however, has sometimes dealt only with GCM sampling informed primarily by history-matching observed state variables in a local domain. That single performance attribute is grossly insufficient to characterize actual model spreads and their effects on the hydroclimatic variables used to identify water-resource climate vulnerabilities. However, time-sensitive, real-world vulnerability studies typically cannot accommodate an entire ensemble of even one link in that combined model chain, so a gap has opened between current scientific knowledge and practice and many routine climate-changed hydrology applications.
To help close that gap the US Army Corps of Engineers, the Bureau of Reclamation, and the National Center for Atmospheric Research have begun collaborative work to subsample uncertainties objectively across model chain components and to integrate results into quantitative hydrologic storylines of climate-changed futures. Importantly, these quantitative storylines are not drawn from a restricted set of models but span a more comprehensive characterization of the full uncertainty space for each model component. Of most significance for water-resource practitioners, these quantitative hydrologic storylines will be anchored in actual design and operations decisions affected by climate change. This talk will describe part of our joint work characterizing variability and uncertainty across model chain components for making the resulting quantitative storylines most useful in practical applications.
Jeff is Senior Scientist and Lead Climate Scientist at the U.S. Army Corps of Engineers (USACE) where he works on the technical and science-policy concerns of climate change for water resource applications. He co-directs the USACE National Climate Preparedness and Resilience programs and leads the agency’s integration of climate change mitigation with climate adaptation from the Joint Institute for the Study of the Atmosphere and Ocean (JISAO) at the University of Washington in Seattle. His own research deals with diagnostic evaluation of process-level sensitivities in the interacting atmospheric and land surface models used to support assessments of climate change threats and impacts.
Jeff’s the immediate past national co-chair of the U.S. Global Change Research Program’s (USGCRP) Adaptation Science Inter-agency Working Group, and previously led work under the Informing Decisions goal for the White House Office of Science and Technology Policy’s (OSTP) Subcommittee on Global Change Research, which directs the work of USGCRP. He was also the U.S. government’s Lead Review Editor for climate adaptation in the IPCC Fifth Assessment Report. Jeff’s a member of the U.S. Environmental Protection Agency’s Board of Scientific Counselors for review of that agency’s air, climate, and energy research programs; and of the Science Advisory Board for the U.S. Department of Energy / Oak Ridge National Laboratory’s Climate Change Science Institute; and of the Committee of Visitors for the U.S. Department of Energy’s Office of Science climate programs.
Jeff serves on national and international proposal and program review committees, is a regular reviewer for journals in the atmospheric and hydrologic sciences, and has more than 60 peer-reviewed publications. He holds a Ph.D. in atmospheric chemistry and physics from the University of North Carolina at Chapel Hill.