USGCRP July17th Seminar: "Greenhouse Concerns: Lessons from the Past"

Tony Socci tsocci at
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 


Dr. Herman Zimmerman, Program Director for Paleoclimatology, National 
Science Foundation, Arlington, VA 


Dr. Thomas J. Crowley, Department of Oceanography, Texas A&M University, 
College Station, TX  -  Title: "Greenhouse Lessons from the Geologic 

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" 


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 

                                               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. 


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 

                   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 

Additional information on the U.S. Global Change Research Program (USGCRP) 
and this Seminar Series is available on the USGCRP Home Page at: Normally these seminars are held on the second 
Monday of each month. 

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