Frontiers of Science
The Frontiers of Science lecture series brings eminent scientists from around the world to the University of Utah and the Salt Lake City community. Lectures start at 6 p.m. and are free and open to the public.
Aline Skaggs Wilmot Building, Room 220 (map)
Check this page often for updates on speakers, lectures, and more information!
Tickets are not required for this event. Seating will be available on a first come, first served basis. Please arrive early.
Thursday, March 26, 2015
Title: Global Climate Change, ENSO, and Black Swans: A Paleoclimate Perspective from the World's Highest Mountains
Featuring: Dr. Lonnie G. Thompson, Distinguished University Professor, School of Earth Sciences at The Ohio State University and Senior Research Scientist, Byrd Polar Research Center
Glaciers serve both as recorders and early indicators of climate change. Over the past 37 years our research team at the Byrd Polar Research Center has recovered climatic and environmental histories from ice cores drilled in both polar regions and from low to mid-latitude, high-elevation ice fields. These ice core derived proxy records, many of which extend back over 25,000 years, have made it possible to compare glacial stage conditions in the tropics with those in the polar regions, as well as more detailed events over the last 1000 years.
Tropical rainfall patterns influence the lifestyles of billions of people both north and south of the equator. High resolution tropical ice core records allow precise examination of climate events on both sides of the Pacific Ocean basin which are often connected by El Niño-Southern Oscillation (ENSO). The effects of major ENSO events, such as droughts, are often recorded in the oxygen isotopic ratios and aerosol concentrations in ice cores. Here we examine unusual events recorded in three ice cores, two of which (Quelccaya and Coropuna) are located in the southern hemisphere on the Peruvian Altiplano while the third (Dasuopu) is located on the southern edge of the Tibetan Plateau at the top of the Himalayas. These ice core records provide evidence that the unique lower and middle tropospheric air flow over chloride (Cl-) and fluoride (F-) enriched areas upwind of the sites during ENSO events, along with drought-related circulation patterns in both these widely separated regions, leads to the enrichment of the anionic species deposited on these glaciers. The records demonstrate linkages between ice-core chemistry and drought indicators, changes in lake levels, and ENSO and monsoon indices. Two unusual events, in the late 18th and mid-14th Centuries, are marked by abnormally high concentrations of F- and Cl-. All of the cores contain evidence of a drought from 1789 to 1800 CE in which increases in these anionic concentrations reflect the abundance of continental atmospheric dust derived from arid regions upwind of the core sites. The earlier event, apparent only in the Quelccaya and Dasuopu ice cores, begins abruptly in 1343 and tapers off by 1375. Neither episode occurs concurrently with major volcanic activity. The interaction between high frequency El Niños and low frequency shifts in the inter-tropical convergence zone may have resulted in these unusually severe and extended droughts. They may have been linked to “Black Swan” episodes corresponding to historically documented, devastating population disruptions which were possibly climate related. Black Swan theory describes rare and unpredictable events that have major historical impacts, but appear explainable in hindsight. The 1789 to 1800 CE event was concurrent with the Doji Bara famine resulting from extended droughts that led to over 600,000 deaths in central India by 1792. Similarly extensive climate disruptions are documented in Central and South America. The mid-14th Century drought, although poorly recorded historically in South America, is concomitant with major monsoon failures in India, the collapse of the Yuan Dynasty in China, and the “Black Death” pandemic that eliminated roughly one third of the global population. Understanding the characteristics and drivers of these historical events is critical in order to design adaptive measures for a world with over seven billion people and unprecedented anthropogenic influence on the climate.
Most climate records from lower latitudes, when taken together, show current warming that is unprecedented for the last two millennia. Indeed, at many alpine sites this warming is unprecedented since the early Holocene. Ice cores retrieved from shrinking glaciers confirm their continuous existence for periods ranging from hundreds to thousands of years, suggesting that current climatological conditions in those regions are different from those under which these ice fields originated and have been sustained. The ongoing widespread melting of high-elevation glaciers and ice caps, from the Antarctic Peninsula to low/middle latitudes, provides strong evidence that a large-scale, pervasive and, in some cases, rapid change in Earth’s climate system is underway. The histories of these ice caps, told through the scientific evidence gained under often challenging conditions from some of world’s most remote regions, provide a global perspective for contemporary climate.