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The Missing Ice Age

The Missing Ice Age
Reported by
Christine Van Lenten

Posted January 11, 2010

Presented By

Atmospheric Sciences & Geology Section and Environmental Sciences Section


Conventional climate science holds that humans first began to influence climate around 200 years ago, when they started burning large amounts of fossil fuels. A new hypothesis, posited by William F. Ruddiman, holds that humans began altering climate around 8000 years ago.

Ruddiman explained his ideas at an Academy meeting on October 25, 2005. He noted that during past periods that followed glaciations, temperatures rose, peaked, and then fell to a threshold that triggered the next glaciation. During these interglaciations, atmospheric levels of two greenhouse gases (GHGs), methane and CO2, rose, then fell. But following the last glaciation, temperatures rose as expected, then started to fall but did not continue to fall. Levels of CO2 and methane rose and continued to rise when they should have fallen.

Web Sites

Domesday Book
Commissioned in 1086, this book compiled the results of a comprehensive survey of England. The Web site devoted to it reports, "It was written by an observer of the survey that 'there was no single hide nor a yard of land, nor indeed one ox nor one cow nor one pig which was left out.'" The Web site will keep you busy.

Lamont Doherty Earth Observatory
Part of Columbia University's Earth Institute, LDEO researchers study Earth on a global scale. Climate is one focus.

NASA Goddard Institute for Space Studies
Part of NASA and Columbia University, GISS furthers research into climate past, present, and future.


Ferretti, D. F., J. B. Miller, J. W. C. White et al. 2005. Unexpected changes to the global methane budget over the past 2000 years. Science 1714-1717.
The authors report that carbon isotopes of methane trapped in Antarctic ice indicate that biomass burning during the past 2000 years has been an unexpectedly major source of methane.

Ruddiman, William F. 2005. Plows, Plagues, and Petroleum: How Humans Took Control of Climate. Princeton University Press, Princeton, NJ.

Ruddiman, W. F. 2005. How did humans first alter global climate? Scientific American (March).

Williams, M. 2002. Deforesting the Earth: From Prehistory to Global Crisis. University of Chicago Press, Chicago.


William F. Ruddiman, PhD


William F. Ruddiman is the author of the college textbook Earth's Climate: Past and Future and of the recently published Plows, Plagues, and Petroleum: How Humans took Control of Climate.

He received a BA in geology in 1964 from Williams College and a PhD in marine geology in 1969 from Columbia University. He recently retired as professor of environmental sciences at the University of Virginia, following many years as a Doherty Senior Scientist at Lamont-Doherty Earth Observatory of Columbia University.

He has published over 110 articles in journals, including several in Scientific American, Nature, and Science. His work on the long-term effect of uplift of the Tibetan plateau on global climate over the last 50 million years was featured in science documentaries that aired on NOVA and the BBC. He has also examined the effects of ice sheet cycles on temperatures in the North Atlantic and across Eurasia.

Christine Van Lenten

Christine Van Lenten has written about public policy issues and technical and scientific subjects for federal and state agencies, nonprofit organizations, and private sector firms.