"Tom Swetnam is renowed for his expertise at using tree-ring records in combination with other natural archives and documentary sources to reconstruct the histories of fire, insect outbreaks, human land uses, and climate. His compelling perspective on climate change also connects to the Bren School's current Strategic Environmental Research Initiative, which is focused on wildfire at the urban-wildlife interface in the arid western United States under climate change. — Steve Gaines, Faculty Host Abstract Extraordinarily large crown fires have burned during recent decades in some western US forests as a consequence of forest and climate changes. Wind events have played important roles in driving major runs during many of these wildfires, including the most rapid burning rates yet recorded in some forests, at more than 40,000 acres per day, over multiple days. Tree rings and fire scars in ancient pines, giant sequoias and bigcone Douglas-fir trees reveal long-term patterns and causes of changes in fire regimes in those forests, including the roles of people and climate variations. Fire atlases and archival satellite imagery spanning the most recent 4 decades show distinctive patterns in forest cover created by wind-driven crown fires, with increasing trends in frequency and run lengths in the Southwestern US. Some of these extremely fast moving and dangerous wildfires exhibited "vortex" behaviors, such as "fire whirls" and enormous, rotating smoke plumes. Changing atmospheric circulation patterns and consequent effects on drought, wind and extreme fire behaviors will likely become more important in coming decades, with multiple implications for fire-fighting strategies and mitigation of risk for communities and watersheds. . Biography Tom Swetnam is Regents' Professor and director of the world's premier center for research and education in dendrochronology at the University of Arizona's Laboratory of Tree-Ring Research in the College of Science. He is a global leader in the study of wildfire and climate history in forest ecosystems, including studies in the superlative coast redwood and giant sequoia groves of California, and the world's most extensive conifer forests in Siberia. His work in recent years has focused especially on the effects of increasing trends in drought and temperatures on forests in the western US and central Siberia. The Zurich Financial Services Distinguished Visitors Program on Climate Change allows the Bren School to attract international leaders in environmental policy, law, business, and science to enrich and expand the intellectual life of the Bren School community and share insight on issues critical to climate change. Activities of the visitors, who are in residence for periods ranging from one week to one quarter, include teaching short courses, offering public lectures, conducting seminars, and leading colloquia and symposia planned around their research, professional endeavors, or areas of expertise.

• published: 08 Jul 2014
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