Abrupt Tropical Climate Change: Past and Present
|Series:||Geoffrey O. Seltzer Lecture|
|Speaker:||Lonnie Thompson, Ohio State|
|Date:||Mon, Nov 7, 2005|
Is the Earth’s climate in the middle of an abrupt change? Has the Earth’s climate changed abruptly in the past? In this talk, I’ll present three examples of abrupt climate change, both past and present, in the tropics. First, there is the current retreat of the world’s glaciers. In the tropics, the retreat is exemplified by the diminishing ice fields on Kilimanjaro, known widely from Hemingway’s novella “The Snows of Kilimanjaro.” Quelccaya (in Peru) is the largest tropical ice cap, and the retreat of its largest outlet glacier, Qori Kalis, actually provides the best documented evidence of global warming in the tropics. Secondly, I’ll describe the ice core records from three Tibetan and three Andean glaciers. These records show how unusual the 20th century is throughout the low-latitude, high-altitude regions of the Earth. Finally, 6,500-year-old remains of wetland plants collected in 2002, 2004, and 2005 place the abrupt climate change that is currently underway in Peru within a longer time perspective; they indicate much warmer conditions in the past. These three lines of evidence argue that, at least in some areas, the present warming and glacier retreat is unprecedented for at least 6,500 years. Simultaneous with 20th- and 21st-century warming, ice masses worldwide are retreating rapidly, contributing to global sea-level rise and threatening fresh water supplies in the world’s most populous tropical regions. I’ll conclude by offering some thoughts on the human response to global climate change.
Thompson is Distinguished University Professor of Geological Sciences
at Ohio State University, and was recently elected a member of the
National Academy of Sciences. He is an expert on the effects that
global climate change is having on the shrinking of glaciers and ice
fields around the globe.