[meteorite-list] Climate Model Links Higher Temperatures to Prehistoric Extinction

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Aug 25 16:25:38 2005
Message-ID: <200508252003.j7PK3Qi22386_at_zagami.jpl.nasa.gov>

http://www.ucar.edu/news/releases/2005/permian.shtml

Contacts for This Release
 
For Journalists
Anatta (anatta_at_ucar.edu), head of Media Relations, 303-497-8604

Jeffrey Kiehl (jtkon_at_ucar.edu), NCAR Climate and Global Dynamics
Division 303-497-1350

Cheryl Dybas (cdybas_at_nsf.gov), NSF Public Affairs 703-292-7734

UCAR Communications
General inquiries
Yvonne Mondragon (yvonnem_at_ucar.edu),
303-497-8601

Head of Visual Services
Nita Razo (razo_at_ucar.edu), 303-497-8606


Climate Model Links Higher Temperatures to Prehistoric Extinction
The National Center for Atmospheric Research
August 24, 2005

BOULDER - Scientists at the National Center for Atmospheric Research
(NCAR) have created a computer simulation showing Earth's climate in
unprecedented detail at the time of the greatest mass extinction in the
planet's history. The work gives support to a theory that an abrupt and
dramatic rise in atmospheric levels of carbon dioxide triggered the
massive die-off 251 million years ago. The research appears in the
September issue of Geology.

"The results demonstrate how rapidly rising temperatures in the
atmosphere can affect ocean circulation, cutting off oxygen to lower
depths and extinguishing most life," says NCAR scientist Jeffrey Kiehl,
the lead author.

Kiehl and coauthor Christine Shields focused on the dramatic events at
the end of the Permian Era, when an estimated 90 to 95% of all marine
species, as well as about 70% of all terrestrial species, became
extinct. At the time of the event, higher-latitude temperatures were
18 to 54 degrees Fahrenheit (10 to 30 degrees Celsius) higher than
today, and extensive volcanic activity had released large amounts of
carbon dioxide and sulfur dioxide into the atmosphere over a
700,000-year period.

To solve the puzzle of how those conditions may have affected climate
and life around the globe, the researchers turned to the Community
Climate System Model (CCSM). One of the world's premier climate research
tools, the model can integrate changes in atmospheric temperatures with
ocean temperatures and currents. Research teams had previously studied
the Permian extinction with more limited computer models that focused on
a single component of Earth's climate system, such as the ocean.

The CCSM indicated that ocean waters warmed significantly at higher
latitudes because of rising atmospheric levels of carbon dioxide (CO2),
a greenhouse gas. The warming reached a depth of about 10,000 feet
(4,000 meters), interfering with the normal circulation process in which
colder surface water descends, taking oxygen and nutrients deep into the
ocean.

As a result, ocean waters became stratified with little oxygen, a
condition that proved deadly to marine life. This in turn accelerated
the warming, since marine organisms were no longer removing carbon
dioxide from the atmosphere.

"The implication of our study is that elevated CO2 is sufficient to lead
to inhospitable conditions for marine life and excessively high
temperatures over land would contribute to the demise of terrestrial
life," the authors concluded in the article.

The CCSM's simulations showed that ocean circulation was even more
stagnant than previously thought. In addition, the research demonstrated
the extent to which computer models can successfully simulate past
climate events. The CCSM appeared to correctly capture key details of
the late Permian, including increased ocean salinity and sea surface
temperatures in the high latitudes that paleontologists believe were 14
degrees Fahrenheit (8 degrees Celsius) higher than present.

Permian
This image shows annual mean surface temperatures in degrees Celsius at
the time of the Permian extinction. It is based on a computer simulation
generated by the Community Climate System Model at NCAR. (Illustration
courtesy Jeff Kiehl, NCAR.)

The modeling presented unique challenges because of limited data and
significant geographic differences between the Permian and present-day
Earth. The researchers had to estimate such variables as the chemical
composition of the atmosphere, the amount of sunlight reflected by
Earth's surface back into the atmosphere, and the movement of heat and
salinity in the oceans at a time when all the continents were
consolidated into the giant land mass known as Pangaea.

"These results demonstrate the importance of treating Earth's climate as
a system involving physical, chemical , and biological processes in the
atmosphere, oceans, and land surface, all acting in an interactive
manner," says Jay Fein, director of NSF's climate dynamics program,
which funded the research. "Other studies have reached similar
conclusions. What's new here is the application of a detailed version of
one of the world's premier climate system models, the CCSM, to
understand how rising levels of atmospheric carbon dioxide affected
conditions in the world's oceans and land surfaces enough to trigger a
massive extinction hundreds of millions of years ago."

Related sites on the World Wide Web

NCAR Climate and Global Dynamics Division home page
<http://www.cgd.ucar.edu/>

------------------------------------------------------------------------

The National Center for Atmospheric Research and UCAR Office of Programs
are operated by UCAR under the sponsorship of the National Science
Foundation and other agencies. Opinions, findings, conclusions, or
recommendations expressed in this publication do not necessarily reflect
the views of any of UCAR's sponsors.
Received on Thu 25 Aug 2005 04:03:25 PM PDT