Climate Models: How Certain are their Projections of Future Climate Change? USGCRP Seminar, 12 June 1995. Page: 1
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'... Climate Models: How Certain are their Projections of Future
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Updated 13 August, 2004 USGCRP Seminar, 12 June 1995
How Are Climate Models Constructed and Tested?
How Have Climate Models Advanced Our
Understanding of the Climate System and of
Potential Climate Change?
SPEAKER: Dr. Eric J. Barron, Pennsylvania State
University, College Park, PA
INTRODUCTION: Dr. Michael C. MacCracken,
Director, Office of the U.S. Global Change
TIME & LOCATION: Mon., June 12, 1995, 3:15pm -
4:45pm, Rayburn House Office Bldg., Room B369 -
In a recent USGCRP-sponsored forum to evaluate
the results of model simulations of climate change,
a cross-section of leading climate and Earth system
modelers and skeptics considered what is known
with certainty, what is known with less certainty,
and what remains uncertain. Following an
introduction to what models are by Dr. Michael
MacCracken, Dr. Eric Barron will describe the
results of the forums conclusions.
What is certain from observations is that the
concentrations of atmospheric greenhouse gases
such as carbon dioxide are increasing due to
human activities. These higher levels will increase
further and persist for centuries.
Projecting the future climatic effects of these
increases requires models. The level of confidence
in the results of thus depends on how well the
climate system can be represented in the models.
These models indicate that it is quite probable that
the globally-averaged surface temperature will
increase by about 2-4 degrees Fahrenheit (1-2
degrees Celsius) by 2050, assuming there are no
significant actions to reduce emissions and no
unusually large natural variations of the climate.
Along with the warming it is very likely that global
mean precipitation will increase, that arctic sea ice
extent will be reduced and adjacent areas will
experience wintertime warming, and that global
sea-level will rise at an increasing rate. Probable
outcomes include: increasing summertime dryness
in the Northern Hemisphere mid-latitudes, an
increase in high-latitude precipitation, and
occasional cooling episodes due to sporadic
volcanic eruptions such as Mt. Pinatubo in 1991.
Models cannot yet tell us with confidence whether
there will be changes in the day-to-day, month-
to-month, or year-to-year variability or what such
changes might be. While regional changes will be
different than the latitudinal average changes,
models also cannot yet estimate what these
regional departures will be nor can they tell us
whether there might be changes in tropical storm
intensity. Other important details also remain
uncertain, awaiting further improvements in climate
models and in the understanding of fundamental
Biography of Dr. Eric J. Barron
Dr. 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
12/18/2009 1:22 PM
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Barron, Eric J. Climate Models: How Certain are their Projections of Future Climate Change? USGCRP Seminar, 12 June 1995., text, June 12, 1995; Washington, D.C.. (digital.library.unt.edu/ark:/67531/metadc11837/m1/1/: accessed April 25, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .