Humans First Altered Climate Thousands (Not Hundreds) of Years Ago

Tuesday, December 5, 2006
Humans First Altered Climate Thousands (Not Hundreds) of Years Ago
Stern Center, Great Room, 7:00 p.m.


Issue in Context
The earth’s climate naturally goes through periods of warming and cooling. Currently, the average temperature of the planet is increasing at an alarming rate. The most common conjecture of environmental scientists is that human actions are accelerating the natural warming of the planet. The amount of greenhouse gases, like carbon dioxide (CO 2 ) and methane (CH 4 ), present in the atmosphere has increased, due in part to human consumption of fossil fuels such as oil, coal and natural gas. Most scientists attribute this increase to the population growth and the industrialization of the past few hundred years in human history. However, William F. Ruddiman, a professor emeritus from the Department of Environmental Sciences at the University of Virginia suggests that significant human intervention in the natural operation in the climate system actually began 5,000 to 8,000 years ago. Even while the world population was relatively small, heavy deforestation and rice irrigation in Eurasia , compounded by additional emissions from an unusually warm ocean caused a shift in global climate. Ruddiman suggests that by the start of the industrial revolution 300 years ago the levels of greenhouse gases were already unusually high.

About the Speaker
William F. Ruddiman is a professor emeritus in the Department of Environmental Sciences at the University of Virginia . His research focuses on the causes of climate change on tectonic, orbital and human time scales. His published works include two books, Earth’s Climate: Past and Future , and Ploughs, Plagues and Petroleum , as well as over 115 articles for peer reviewed scientific journals. He is a fellow of both the Geological Society of America and the American Geophysical Union. Ruddiman has worked as an oceanographer for the U.S. Navy and has held a number of research positions, including associate director and Doherty Senior Research Scientist at the Lamont-Doherty Earth Observatory of Columbia University. He was director of the research program CLIMAP, (Climate/Long Range Investigation Mappings and Predictions Project) from 1982-1983 and served on the executive committee of COHMAP ( Cooperative Holocene Mapping Project ) from 1982-1990. Both these programs focused on utilizing oceanic and glacial data to study the earth’s climate pattern. Ruddiman served on many committees including National Science Foundation’s Earth System History Steering Committee and IGBP PAGES (Past Global Changes) Committee. Among other honors, he was featured in the 1997 NOVA Film: “Cracking the Ice Ages.” Ruddiman received his bachelor’s degree in geology from Williams College and his doctorate in marine geology from Columbia University.

Related Links

US EPA Global Warming Site

Global Warming Research Explorer- The Exploritorium

Intergovernmental Panel on Climate Change

NCDC: Global Climate Change

BEYOND THE IVORY TOWER: The Scientific Consensus on Climate Change