USGCRP July17th Seminar: "Greenhouse Concerns: Lessons from the Past"
Tony Socci
tsocci at usgcrp.gov
Thu Jul 11 17:12:46 EDT 1996
U.S. Global Change Research Program Second Monday Seminar Series
Greenhouse Concerns: Lessons from the Past
What geological insights do the records of climate change provide
regarding the potential influence on climate of the increases in greenhouse
gas concentrations? How well do we understand what has caused past changes
in climate? How well do models reproduce these past climate changes? What
do these studies tell us about how sensitive the climate is to changes in
the composition of the atmosphere?
Public Invited
Wednesday July 17, 1996, 3:15-4:45 PM
Rayburn House Office Bldg., Room B354
Reception Following
Please Note the Change in Room Location
INTRODUCTION
Dr. Herman Zimmerman, Program Director for Paleoclimatology, National
Science Foundation, Arlington, VA
SPEAKERS
Dr. Thomas J. Crowley, Department of Oceanography, Texas A&M University,
College Station, TX - Title: "Greenhouse Lessons from the Geologic
Record"
Dr. Eric Barron, Director of the Earth System Science Center, Pennsylvania
State University, College Park, PA - Title: "Climate Sensitivity: A
Perspective from Paleoclimate Model Applications"
Overview
The importance of studying Earth History stems from the unique insights
that can be drawn. Such studies can document the natural climate and its
rates of change and variability prior to human activity; can be used to
estimate the sensitivity of the Earth's climate system to changes in carbon
dioxide, volcanic eruptions, and changes in the land surface; can be used
to test the reliability of climate models by evaluating their simulations
for conditions very different from the modern climate; and can be used to
examine the integrated climate, chemical, and biological responses of the
Earth to a variety of perturbations. Studies of Earth system history are
best done by combining and reconciling the findings from observational and
analytical studies with integrating studies using numerical models of the
climate.
Paleoclimate Observations
The geological history of the Earth provides strong evidence that climate
has changed on time scales of decades to millions of years. Understanding
this history can provide a basis for evaluating projections of climate
change due to anthropogenic greenhouse perturbations and provide a context
for human influences amongst the archive of natural perturbations of
climate. Dr. Crowley will provide examples of how climate has changed on a
variety of timescales and will highlight some of the lessons that can, and
have, been learned by examining past records of climate change. For
example, projections of warming for the next century suggest that
temperatures will approach levels that have not occurred in many millions
of years. The rapidity of this projected warming is greater than has
occurred in the past and will lead to a very different climate state than
exists today. The Earth's geological record also suggests that changes in
the atmospheric concentrations of CO2 have contributed significantly to
past climate changes, underscoring the importance of the role of CO2 in
determining the climate state.
Paleoclimate Models
Two aspects of the study of Earth history with models (referred to as
paleoclimatic modeling) are particularly valuable. First, comparison of
climate model simulations of past climatic periods with geologic data
suggest that for some variables (e.g., storm tracks) the climate models
evidently yield robust predictions even for conditions very different from
the present day climate. For other variables, such as regional
precipitation, the model predictions are not yet representing the estimated
regional patterns that have been developed from the geological record.
Second, a variety of past climatic periods can be utilized as "case
studies" of climate sensitivity. For these cases, the consistency of the
estimates of climate sensitivity to carbon dioxide variations described in
the recent IPCC Second Assessment report are comparable to the
sensitivities required to explain the geologic record. In other words, the
geologic record offers the opportunity to assess some of the limitations
and strengths of climate model predictions, as well as to assess climate
sensitivity to changes such as increases in greenhouse gases. While
uncertainties exist, in each case analyzed to date, the geologic record
suggests that the mid to upper range of climate sensitivity given by the
IPCC report is most reasonable.
Biographies
Dr. Thomas J. Crowley has held a number of positions in paleoclimatology:
assistant professor at the University of Missouri - St. Louis, program
director in climate dynamics at the National Science Foundation, National
Research Council Fellow at NASA/Goddard Space Flight Center, senior
scientist for the Applied Research Corporation, and most recently Professor
of Oceanography at Texas A&M University. Although his early work involved
the study of the North Atlantic Ocean circulation during the last ice age,
he has subsequently become interested in the effects of the movement of
continents on climate, both from a modeling and observational viewpoint.
Dr. Crowley has also been involved in several studies synthesizing
paleoclimate data, especially with respect to its relevance to better
understanding future climate projections due to the anthropogenic
greenhouse perturbation. He is the author of a number of articles on past
climates and is co-author of a recent book on the subject. Dr. Crowley
received his Ph.D. in marine geology from Brown University in 1976.
Dr. Eric Barron is Professor of Geosciences and Director of the Earth
System Science Center at Pennsylvania State University in College Park PA.
He also serves as chair of the Climate Research Committee of the National
Research Council, chair of the National Science Foundation Advisory
Committee on Earth System History, and editor of Global and Planetary
Change. Dr. Barron has degrees in geology from Florida State University and
in oceanography and climate from the Rosenstiel School of Marine and
Atmospheric Sciences at the University of Miami. He has been awarded the
Smith Prize (University of Miami), the Wilson Research Award and the
Provost's Award for Innovation in Teaching (PSU), and is a fellow of the
American Geophysical Union. Dr. Barron served as Chair of the U. S. Global
Change Research Program's Forum on Global Change Modeling held in October
1994.
The Next Seminar is scheduled for Monday, September 16, 1996
Watch the USGCRP home page for information on the topic.
For more information please contact:
Dr. Anthony D. Socci, U.S. Global Change Research Program Office
300 D St., SW, Suite 840, Washington, DC 20024
Telephone: (202) 651-8244; Fax: (202) 554-6715
E-Mail: TSOCCI at USGCRP.GOV.
Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. Normally these seminars are held on the second
Monday of each month.
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