I have been serving as chief scientist of the Atmospheric Science Program since its reconfiguration, in mid-2004, to its present focus on radiative forcing by atmospheric aerosols. For information on the program, present and planned activities, and links to presentations and publications and the like, please visit the program web page http://www.asp.bnl.gov.
Much of our recent research has focused on the radiative influence of anthropogenic aerosols on climate in connection with the larger issue of possible human-induced climate change, the so-called global warming issue (139K pdf
Estimates from the IPCC (Intergovernmental Panel on Climate Change) Report Climate Change 2001 on of the several contributions to radiative forcing over the industrial period are shown in the following figure. (The unit of forcing, and of energy fluxes in geophysics generally, is the watt per square meter.) Also shown (as "I-beams") are the IPCC's estimates of the uncertainties associated with each of these quantities. It is seen that the uncertainties of the several aerosol forcings substantially exceed those associated with the greenhouse gases and other forcings; note that the IPCC declined even to provide an estimate for the indirect forcing, giving only an indication of the range of possible values. Note also the labels under the several bars denoting the IPCC's confidence that the actual forcing lies within the range indicated by the uncertainties.
From
"Uncertainty requirements in radiative forcing of climate change,"
S. E. Schwartz, J. Air Waste Management Assoc. 54, No. 11, (November, 2004). (800K pdf
Attention is called to the several bars at the right of the figure denoting the total aerosol forcing and the total forcing and the associated uncertainties. These forcings were not evaluated by IPCC but were evaluated from the IPCC estimates of the individual forcings. The first bar denotes total aerosol forcing evaluated as algebraic sum of IPCC aerosol forcings, with mineral dust and aerosol indirect forcings taken as zero; for the second bar these forcings were taken as the mid-points of the IPCC uncertainty ranges. The third and fourth bars denote total forcing evaluated in the same way, again with mineral dust and aerosol indirect forcings taken as zero and as the mid-points of the IPCC uncertainty ranges, respectively.
For each bar two uncertainty estimates are provided. For the first (larger) uncertainty estimates the upper and lower limits of the uncertainty range were calculated as the algebraic sum of upper and lower limits, respectively, of the uncertainties of the several forcings. For the second (smaller) uncertainty estimates the upper and lower limits of the range were calculated as the square root of the sum of the squares, respectively, of the of the upper and lower uncertainty ranges relative to the estimated forcings denoted by the bars. No matter how the uncertainties are calculated, they are quite large relative to the estimated total forcing over the industrial period. In view of these uncertainties, which are due largely to uncertainty in aerosol forcing, it cannot be stated with certainty that the warming influences of CO2 and other GHGs exceeds the cooling influences due largely to aerosols, although this is likely to be the case.
It should be emphasized that one should not take any comfort with the fact that the aerosols may be negating much of the greenhouse gas forcing--in fact just the opposite. Because the atmospheric residence time of tropospheric aerosols is short (about a week) compared to the decades-to-centuries lifetimes of the greenhouse gases, then to whatever extent greenhouse gas forcing is being offset by aerosol forcing, it is last week's aerosols that are offsetting forcing by decades worth of greenhouse gases. Because the greenhouse gases are long-lived in the atmosphere, their atmospheric loadings tend to approximate the integral of emissions. Because the aerosols are short-lived, their loading tend to be proportional to the emissions themselves. There is only one function that is proportional to its own integral, the exponential function. So only if society is to make a commitment to continued exponential growth of emissions can such an offset be maintained indefinitely. And of course exponential growth cannot be maintained forever. So if the cooling influence of aerosols is in fact offsetting much of the warming influence of anthropogenic greenhouse gases, then when society is unable to maintain this exponential growth, the climate could be in for a real and long-lasting shock.
Because uncertainties associated with aerosol forcing are the major source of uncertainty in climate forcing over the industrial period, it is crucial in my opinion to focus on the aerosol forcing if any progress is to be made in understanding anthropogenically induced climate change. Consequently much of our research is directed to developing such improved understanding.
In a number of studies we have tried to provide estimates of the uncertainty budget associated with the aerosol forcing. Much of the uncertainty arises from the fact that unlike the long-lived greenhouse gases, whose concentrations are rather uniformly distributed in the atmosphere, the loadings of aerosols are highly variable in space and time, as a consequence of highly localized sources and of sporadic removal, mainly by precipitation. Additionally aerosol microphysical properties are not a universal constant, but depend on sources and composition and evolve as a consequence of chemical and physical processes occurring in the atmosphere. The mass loading, composition, and the microphysical properties of aerosols such as number concentration and size distribution directly affect their direct and indirect radiative forcing of climate.
Reducing the uncertainty in aerosol forcing will require a major effort both in characterizing the present distribution and properties of aerosols and in developing understanding required to represent the processes controlling loading and properties of tropospheric aerosols in numerical models. Model-based descriptions of aerosol forcing need to be incorporated into climate models in order to represent this forcing not just for the present climate but also retrospectively over the industrial period and prospectively for various scenarios of future emissions. Much of our research is directed to developing and evaluating numerical models for representing the geographical distribution of loading of atmospheric aerosols. Our approach has been to use observationally derived meteorological data to drive our models, because the temporal and spatial variation in aerosol loading is governed to great extent by meteorological variability. Meaningful evaluation of the model by comparison with observations thus requires this approach. Much of this work is conducted within the Department of Energy's Atmospheric Science Program (ASP).
An additional major component of our research is directed to developing improved representation of aerosol optical properties and radiative forcing. Much of this work is conducted in conjunction with the Department of Energy's Atmospheric Radiation Measurement (ARM) Program.
For a quick tour of Aerosol Research at BNL click
here (900K pdf
Our work is represented in our
publications. I welcome inquiries of interest from any and all. Much of our work is conducted in collaboration with others at their institutions or as visiting scientists at Brookhaven National Laboratory. I particularly encourage inquiries from students; you are our future.
A riddle that's gained some currency in our group: "What's black and white and red all over?"
Answer
The DOE Office of Science 1999 Strategic Plan included a section on the climate influence of aerosols, highlighting our research. To download just this section (600 K pdf
Modeling atmospheric sulfate on subhemispheric to hemispheric scale. Our group has developed (and continues to develop) a chemical transport model for atmospheric sulfate and precursor species. The output of this model is mixing ratios of sulfate as a function of location and time. The model is driven by observationally derived meteorological data (archived numerical weather prediction forecast model results) so the modeled sulfate may be compared with observations at specific locations and times.
Modeling sulfate on hemispheric scale. This link connects to movies generated with output from our model showing the evolution of column burden of sulfate from Asian anthropogenic sources and of total sulfate as a function of location in the Northern Hemisphere, June-July 1997.
Modeling volcanic sulfate on hemispheric scale. This link connects to a movie generated with output from our model showing the temporal and spatial evolution of column burden of sulfate from volcanic SO2 emissions in the Northern Hemisphere, June-July 1997.
Aerosol Perturbations on Climate. Our model runs on computers at NERSC (National Energy Research Scientific Computing Center). Our work was featured in the climate modeling section of the 1998 NERSC Annual Report .
Grains of Salts. An account of our work presented in a plenary lecture at the 1997 annual meeting of the American Association of Aerosol Research was featured in the February 1998 issue of ER News, Newsletter of the Department of Energy's Office of Energy Research.
High-Resolution Model for Tropospheric Sulfate. Our model for tropospheric sulfate was highlighted in a DOE Research Summary (November 1994).
Atmospheric Heating and Cooling from Fossil-Fuel Combustion. Our examination of the greenhouse heating influence of fossil fuel combustion versus the aerosol cooling influence was highlighted in the Fall 1994 Newsletter of the DOE Carbon Dioxide Information and Analysis Center CDIAC Communications.
Things Are Heating Up, The North Shore Sun, September 06, 2007
The Aerosol Man, The National Post, September 01, 2007
CURRICULUM VITAE
Scientist, 1977-90
Senior Scientist, 1990-
Adjunct Professor (Institute for Terrestrial and Planetary Atmospheres), 1994-97
Books: Authored, 1; edited, 2
Journal articles and book chapters, 115
Proceedings and abstracts, 185
Reports and reviews, 40
NSF Graduate Fellow 1963-67
Woodrow Wilson Fellow (Hon.) 1963-64
Ramsay Memorial Fellow, 1968-69
Science and Technology Award, Brookhaven National Laboratory, 2006.
Fellow, American Geophysical Union, 2005.
Haagen-Smit Award for an "Outstanding paper" published in
Atmospheric Environment, 2003. BNL News Release
Fellow, American Association for the Advancement of Science, 2002. BNL News Release
Plenary Lecture, 16th International Conference on Nucleation and Atmospheric Aerosols, Kyoto, 2004
Plenary Lecture, 16th Annual Meeting, American Association for Aerosol Research, Denver, 1997
Plenary Lecture, 14th International Conference on Nucleation and Atmospheric Aerosols, Helsinki, 1996
Editor's Citation for Excellence in Refereeing, Journal of Geophysical Research - Atmospheres, 1995, 2002
Sigma Xi, 1969 (University of California, Berkeley)
Phi Beta Kappa, 1963 (Harvard College)
American Association for Aerosol Research
American Chemical Society and its Divisions of Physical Chemistry and Environmental Chemistry
American Geophysical Union (Fellow)
American Meteorological Society
American Physical Society
Gesselschaft für Aerosolforschung
International Union for Pure and Applied Chemistry (Fellow)
Department of Energy Atmospheric Science Program
Research
Publications and Presentations
Recent Popular Lectures
Research Highlights on the Web
In the News
Curriculum Vitae
Biography
Education and Honors
Memberships
Professional Activities
ATMOSPHERIC SCIENCE PROGRAM
The Department of Energy's Atmospheric Science Program has as its long-term goal developing comprehensive understanding of the atmospheric processes that control the transport, transformation, and fate of energy related trace chemicals and particulate matter. The current focus of the program is aerosol radiative forcing of climate: aerosol formation and evolution and aerosol properties that affect direct and indirect influences on climate and climate change.
file). Aerosols affect the earth's radiation budget directly, by scattering incoming shortwave (solar) radiation and thereby enhancing the earth's albedo, and indirectly, by modifying the microphysical properties and reflectivity of clouds. We and others have presented a body of work over the past decade that indicates that anthropogenic aerosols are exerting an influence on climate change that is comparable (but of opposite sign) to the anthropogenic greenhouse effect. However the magnitude of these aerosol influences is quite uncertain in comparison to that of longwave (thermal infrared) radiative forcing by incremental concentrations of greenhouse gases (mainly carbon dioxide and to lesser extent methane, nitrous oxide, and others) resulting from industrial activity.
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The batting average paradox. Able has a higher batting average than Baker in the first half of the season and also in the second half. You might think that that means that Able has a higher average for the season. But you would be wrong. Click here to see why averaging ratios can be misleading.
file) click here.
Animation of the model results brings out features of the calculations and their temporal evolution that are not readily discernible from static images. We have pioneered in publication of such animations in a peer-reviewed electronic journal.
Dynamical influences on the distribution and loading of SO2 and sulfate over North America, the North Atlantic and Europe in April 1987. Benkovitz C. M., Miller M. A., Schwartz S. E. and Kwon O-U. Geochem. Geophys. Geosyst. 2, Paper no. 2000GC000129 (2001). http://www.agu.org/journals/gc/gc0106/2000GC000129/fs2000GC000129.html.
Modeling atmospheric sulfate on subhemispheric scale. This link connects to Quicktime (R) movies generated with output from our model showing the evolution of column burden of atmospheric sulfate (vertical integral of concentration) over several one-month periods.
IN THE NEWS
A sampling of recent news articles about our work
STEPHEN E. SCHWARTZ
PRIMARY APPOINTMENT
Brookhaven National Laboratory
Senior Scientist
Atmospheric Sciences Division
Environmental Sciences Department
Brookhaven National Laboratory, Upton, N.Y. 11973
Telephone: (631) 344-3100 FAX (631) 344-2887 E-mail ses@bnl.gov
PROFESSIONAL EXPERIENCE
Brookhaven National Laboratory
Associate Scientist, 1975-77
Stony Brook University (State University of New York at Stony Brook)
Assistant Professor (Chemistry), 1969-75
Energieonderzoek Centrum Nederland (Netherlands Energy Research Foundation, ECN)
Visiting Scientist, 1996
PUBLICATIONS
BIOGRAPHYHarvard College
A.B. 1963 Magna cum laude
Ph.D. 1968 with H. S. Johnston
University of California, Berkeley
Fulbright Post-Doctoral Fellow 1968-69 with B. A. Thrush
University of Cambridge, England
ISI Highly Cited Researcher, Thompson Scientific, 2006.
HONORS
Associate Editor, Atmospheric Environment, 1984-95.
Committee on Atmospheric Chemistry, American Meteorological Society, 1985- 91.
Associate Editor, Journal of Geophysical Research - Atmospheres, 1986-89.
Committee on Atmospheric Chemistry, National Research Council, 1988-91.
Management Team, Atmospheric Radiation Measurement (ARM) Program, Department of Energy, 1990-99.
Primary Co-author, "Atmospheric Process Research and Development", Report 2 of Acidic Deposition: State of Science and Technology, U. S. National Acid Precipitation Assessment Program, Washington DC, 1991.
North American Editor/Chemistry and Editorial Advisory Board, Urban Atmosphere, 1991-95.
Co-chair, Fifth International Conference on Precipitation Scavenging and Atmosphere-Surface Exchange Processes, Richland WA, 1991, and Coordinator (with W. G. N. Slinn) of proceedings, published as Precipitation Scavenging and Atmosphere-Surface Exchange, (Hemisphere, Washington DC, 1992).
International Union of Pure and Applied Chemistry, Commission on Atmospheric Chemistry, Associate Member, 1991-94; Titular Member, 1995-98 ; Interdivisional Committee on Nomenclature and Symbols, International Union of Pure and Applied Chemistry, Titular Member, 1998- .
Contributing Author, 1992 IPCC Supplement, Intergovernmental Panel on Climate Change, 1992.
Invited participant, Mission to Washington--Joint Appeal by Religion and Science for the Environment, U. S. Senate, Washington DC, 1992.
Editorial Advisory Board, International Journal of Chemical Kinetics, 1993-95.
Panel on Atmospheric Effects of Stratospheric Aircraft, National Research Council, 1993.
Steering Committee, ACE-2 (Aerosol Characterization Experiment: Radiative Forcing due to Aerosols over the Polluted North Atlantic Region), 1993-97.
Invited witness, Aerosols and Climate, Hearing on the Science Concerning Global Climate Change, Committee on Energy and Natural Resources, U. S. Senate, Washington, DC, 1994.
Co-chair, Gordon Research Conference, Atmospheric Chemistry, Newport RI, 1995.
Spotlight Lecture, Colby College, Waterville, ME, 1996.
Advisory Board, Tellus B, 1997- .
American Geophysical Union, Committee on Global Environmental Change, 1994-98, and Climate Change Panel, 1998. This committee and panel drafted the 1998 AGU Position Statement on Climate Change and Greenhouse Gases. For reaction to this statement, including a statement by then Vice President Gore, click here.
President, Brookhaven Organization of Scientists, 1997-99.
Co-Convener, Symposium on Physical and Atmospheric Chemistry in Honor of Harold Johnston, American Chemical Society, Division of Physical Chemistry, San Francisco CA, 2000.
Steering Committee, Sixth International Conference on Air-Surface Exchange of Gases and Particles, Edinburgh, UK, 2000.
Contributing Author, "Aerosols, their Direct and Indirect Effects" and "Radiative Forcing of Climate Change" in Climate Change 2001 - The Scientific Basis, Intergovernmental Panel on Climate Change.
Lead Scientist, Tropospheric Aerosol Program (TAP), U. S. Department of Energy, 2000-2004.
Scientific Steering Committee, National Aerosol-Climate Interactions Program. (NACIP), 2001- .
Chief Scientist, Atmospheric Science Program (ASP), U. S. Department of Energy, 2004- .
Science Board, ARM (Department of Energy Atmospheric Radiation Measurement Program) Climate Research Facility, 2004-2006.
This page was last updated 2007-10-29.