Knowledge of the adjustment time of anthropogenic CO2, the e-folding time by which excess CO2 (above preindustrial) would decrease in the absence of anthropogenic emissions, is central to understanding the influence of anthropogenic CO2 on climate change and to prospective control of CO2 emissions to reach desired targets. Estimates of this adjustment time from current carbon-cycle models range from about 100 years to over 700 years. This talk examines the CO2 budget by a top-down, observationally based approach. Major stocks and fluxes are quantified. The net flux from the atmosphere and the ocean mixed layer, which are in near equilibrium, to the deep ocean and terrestrial biosphere is found to be proportional to the excess CO2 in these compartments over the Anthropocene. These observations, together with knowledge of the underlying physical and chemical processes, are used to develop a simple, transparent model that describes the transport of CO2 between major compartments -- the atmosphere, the mixed-layer ocean, the deep ocean, and the terrestrial biosphere. This model compares well with observed atmospheric CO2 from 1750 to the present. The adjustment time of excess CO2, evaluated by multiple means including the 1/e decay time and the negative inverse of the fractional annual transfer rate of excess CO2 into the terrestrial biosphere and the deep ocean, is found to be 54 ± 10 years. Such a short adjustment time, if correct, would mean that the atmospheric amount of CO2 would respond quickly and strongly to emission changes. For example, atmospheric CO2 could be immediately stabilized at its present value by decreasing anthropogenic emissions by about 50%.
 
About the Speaker:

Stephen E. Schwartz is a senior scientist at Brookhaven National Laboratory. His current research interest centers on the influence of energy related emissions on climate, with a focus on the role of atmospheric aerosols.

Schwartz is a fellow of the American Association for the Advancement of Science and of the American Geophysical Union, and is recipient of the 2003 Haagen-Smit Award for an "outstanding paper" published in the journal Atmospheric Environment. In 2006 he received the BNL Science and Technology Award for distinguished contributions to the Laboratory's science and technology mission, and in 2010 he received an Outstanding Leadership Award from the U.S. Department of Energy.

In his research at Brookhaven National Laboratory, Schwartz developed methods to describe the rate of reactions in clouds that lead to production of acid rain. Schwartz's research exerted a major influence on the drafting of the acid deposition section of the 1990 Clean Air Act Amendments. More recently, Schwartz has been focusing on microscopic and submicroscopic aerosol particles, which influence a variety of atmospheric processes, from precipitation to climate change.

Schwartz is author or coauthor of over a hundred papers published in peer-reviewed scientific journals. He was editor of Trace Atmospheric Constituents published by Wiley in 1983 and was co-editor of a three volume series Precipitation Scavenging and Atmosphere-Surface Exchange, published by Hemisphere in 1992. He is coauthor of Sea Salt Aerosol Production: Mechanisms, Methods, Measurements, and Models -- A Critical Review, published by the American Geophysical Union in 2004. Schwartz's research has been quite influential. In 2001 he was one of some 350 scientists worldwide to be designated a "highly cited researcher" in geophysics by Thomson-ISI (then the Institute for Scientific Information).

Schwartz has served on numerous national and international panels. As a member of the Committee on Atmospheric Chemistry of the American Meteorological Society he was principal author of that society's 1989 statement on Acid Deposition, and as a member of the Climate Change Panel of the American Geophysical Union he contributed to that organization's seminal 1998 Position Statement on Climate Change and Greenhouse Gases. He has been a contributing author to the 1992, 1995, 2001, and 2007 assessment reports of the Intergovernmental Panel on Climate Change.

Schwartz served as chief scientist of the Department of Energy's Atmospheric Science Program from 2004 through 2009. He also served on the management team which developed and led the Department of Energy's Atmospheric Radiation Measurement (ARM) Program, from the inception of that program in 1990 until 1999.

Schwartz has served on the editorial boards of several atmospheric and chemical journals including Atmospheric Environment (of which he was North American editor for Urban Atmospheres), The Journal of Geophysical Research (Atmospheres), Tellus B (Chemical and Physical Meteorology), and the International Journal of Chemical Kinetics. He has twice been the recipient of the Editor's Citation for Excellence in Refereeing for the Journal of Geophysical Research - Atmospheres.

Schwartz received his bachelor's degree in chemistry from Harvard University, in 1963, and his Ph.D. in chemistry from the University of California, Berkeley, in 1968. After postdoctoral research at the University of Cambridge, England, Schwartz joined the Chemistry Department at Stony Brook University. He joined Brookhaven National Laboratory in 1975. 
                   
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