Purdue Climate Change Research Center

2013 PCCRC Distinguished Lecture

April 29, 2013

Professor David Archer presents, "The Impact of Fossil Fuel Combustion on Earth’s Carbon and Methane Cycles."
Burton Morgan Center, Room 121
May 16, 2013

When fossil fuel CO2 is released to the atmosphere, it essentially accumulates in the relatively rapidly cycling atmosphere/ocean/land biosphere carbon cycle. The atmospheric concentration of CO2 spikes through a time period of CO2 emissions, then is expected to slowly decline over the centuries as CO2 invades the ocean. The "lifetime" of fossil fuel CO2 in the atmosphere is a complicated question because there are multiple processes operating, but in general the CO2 concentration will be higher than natural for hundreds of thousands of years.   Some components of the climate system, such as the ice sheets in Antarctica and Greenland, will respond most strongly to the "long tail" of the fossil fuel CO2, ultimately raising sea level by 10's of meters, something like 100 times more than the IPCC forecast for the year 2100. The interaction of the long tail with orbital forcing has the capacity to alter the trajectory of the glacial / interglacial cycles for hundreds of thousands of years into the future.

Methane released to the atmosphere is oxidized to CO2 on a time scale of about a decade. The concentration in the atmosphere is determined by a dynamic balance between its sources and sinks. The ongoing loss of methane keeps its concentration much lower than that of CO2, eliminating any cumulative effect to that of the oxidation product, CO2, but also lessening the “band saturation effect” for methane, making it a more powerful greenhouse gas than CO2 per molecule. Dr. Archer will discuss the usefulness of limiting methane vs. CO2 emissions, the possibility of a methane feedback to CO2-induced climate change, and the possible role of the permafrost and methane hydrate carbon pools in the carbon cycle of the distant future.

ABOUT THE LECTURER:  David Archer is a professor in the Department of the Geophysical Sciences at the University of Chicago and a Fellow of the American Geophysical Union, publishing on Earth’s carbon cycle and its interaction with global climate. Dr. Archer has written a series of books on climate change, including Global Warming: Understanding the Forecast, a text for non-science major undergraduates now in its second edition; The Long Thaw: How Humans are Changing the Next 100,000 Years of Earth’s Climate; The Climate Crisis, a Summary of the IPCC Scientific Assessment; The Global Carbon Cycle, a primer in climate science; and The Warming Papers: The Scientific Foundation for the Climate Change Forecast. He teaches classes on global warming, environmental chemistry, and global biogeochemical cycles, and is a regular contributor to the climate science blog site realclimate.org.

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