In article <bnuvdi$1n6$1@pencil.math.missouri.edu>, Eric Stewart says...

----- Forwarded message from Eric Stewart <tatteredflag@linuxmail.org> -----
   Date: Thu, 30 Oct 2003 17:06:59 -0700
   From: Eric Stewart <tatteredflag@linuxmail.org>
Reply-To: Eric Stewart <tatteredflag@linuxmail.org>
Subject: Evidence Of Global Warming In The Past Supports Greenhouse Theory
     To: Eric Stewart <tatteredflag@linuxmail.org>

http://www.spacedaily.com/news/climate-03zg.html

Evidence Of Global Warming In The Past Supports Greenhouse Theory
Santa Cruz - Oct 24, 2003

Scientists have filled in a key piece of the global climate picture for a 
period 55 million years ago that is considered one of the most abrupt and 
extreme episodes of global warming in Earth's history. The new results from 
an analysis of sediment cores from the ocean floor are consistent with 
theoretical predictions of how Earth's climate would respond to rising 
concentrations of greenhouse gases in the atmosphere.
The new study, led by James Zachos, professor of Earth sciences at the 
University of California, Santa Cruz, will be published online by Science 
Express on October 23, and will appear in a later print edition of Science 
magazine.

The researchers analyzed sediments deposited on the seafloor during a 
period known as the Paleocene-Eocene Thermal Maximum, when a massive 
release of heat-trapping greenhouse gases is thought to have triggered a 
runaway process of global warming. Climate theory predicts that the 
increase in greenhouse gases would have caused temperatures to rise all 
over the planet, with greater increases in sea surface temperatures at high 
latitudes than at low latitudes.

Zachos and a team of researchers at UCSC and several other institutions 
have now obtained the first reliable estimates of the change in tropical 
sea surface temperatures during this period. When combined with existing 
records of sea surface temperatures at high latitudes, the findings fit 
well with the predictions of computer simulations based on current climate 
theory.

The study provides important backing for the climate models that scientists 
are using to predict the effects of the current rise in atmospheric carbon 
dioxide due to industrial emissions, Zachos said.

"The predictions from the models seem to be consistent with the geologic 
record, so I'd say greenhouse climate theory is alive and well," he 
said. "People have raised questions about how accurate these models are in 
terms of handling heat transport in response to rising greenhouse gases, 
but this study indicates that the climate people have got it right or close 
to right."

The Paleocene-Eocene Thermal Maximum, starting about 55 million years ago 
and lasting about 150,000 years, is marked by dramatic changes in the 
fossil record of life in the ocean and on land. Average global temperatures 
increased by about 5 degrees Celsius (9 degrees Fahrenheit). The increase 
in sea surface temperatures at high latitudes was 8 to 10 degrees Celsius, 
and the new study shows a 4- to 5-degree Celsius increase in tropical sea 
surface temperatures.

"This event is the best example of greenhouse warming in the geologic 
record, and for the first time we have been able to document the climate 
response on a relatively broad planetary scale, from the tropics to polar 
latitudes," Zachos said.

The temperature estimates were derived from chemical analyses of the shells 
of microscopic plankton preserved in the seafloor sediments. The chemical 
composition of the plankton's calcite shells reflects the temperature of 
the water in which they were formed. A key measurement examined in this 
study was the ratio of magnesium to calcium, which increases exponentially 
with the temperature at which the shells formed.

"The ratio of magnesium to calcium in seawater is relatively constant over 
the timescale of this event, so the ratio in the shells is really only 
sensitive to one variable, the calcification temperature," Zachos said.

UCSC graduate students Michael Wara and Steven Bohaty performed most of the 
chemical analyses. The researchers analyzed sediment cores recovered from a 
site called Shatsky Rise in the tropical Pacific during an expedition of 
the ship JOIDES Resolution in 2001 (Leg 198 of the Ocean Drilling Program). 
The cores provided a complete sequence of deposits representing the 
boundary between the Paleocene and Eocene epochs.

"There aren't many places in the Pacific where you can recover sediments of 
this age in which the fossils are not so recrystallized that they've lost 
their original geochemical signatures," Zachos said.

ODP Leg 198 and a complementary drilling expedition in the Atlantic earlier 
this year (ODP Leg 208) were designed to test the leading explanation for 
the Paleocene-Eocene Thermal Maximum, which attributes it to a massive 
release of methane. Methane, a potent greenhouse gas, accumulates in frozen 
deposits known as clathrates found in the deep ocean near continental 
margins and also in the Arctic tundra. For reasons that remain unclear, the 
clathrates suddenly began to decompose, releasing an estimated 2,000 
gigatons (2 trillion tons) of methane.

Once released, the methane would have reacted with dissolved oxygen in the 
ocean to produce carbon dioxide, another greenhouse gas. Large amounts of 
both carbon dioxide and methane would have entered the atmosphere, raising 
temperatures worldwide.

In addition to Zachos, Wara, and Bohaty, the coauthors on the Science paper 
are Margaret Delaney, professor of ocean sciences at UCSC, Maria Rose 
Petrizzo and Isabella Premoli-Silva of the University of Milan, Amanda 
Brill of the University of North Carolina, and Timothy Bralower of 
Pennsylvania State University. Bralower and Premoli-Silva were co-chief 
scientists on ODP Leg 198.

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