Ancient Snail Shells Hint at Future Global Warming
By Stephanie Pappas, LiveScience Senior Writer | LiveScience.com – 1 hr 50 mins agoRelated Content
View PhotoShells of the freshwater gastropod …
A major global cooling event 34 million years ago chilled land as well
as sea, according to climate clues found in an unusual place: fossil
snail shells.
The new research, published today (April 22) in the journal Proceedings of the National Academy of Sciences, reveals the historical links between carbon dioxide
in the atmosphere and surface temperatures on Earth. Between about
333.5 million years ago and 34 million years ago, the climate
transitioned from the balmy, carbon-dioxide-rich Eocene epoch
climate to the cooler, low-carbon-dioxide Oligocene epoch. Scientists
estimate that concentrations of carbon dioxide in the atmosphere dropped
from 1,000 parts per million to about 600 to 700 parts per million in
this time frame.
During this time, ice sheets emerged over Antarctica
and the ocean cooled by some 9 degrees Fahrenheit (5 degrees Celsius).
Researchers have been able to peg ocean temperatures accurately using
cores of rock and mud drilled from the deep ocean. Figuring out what was
happening on land has been more difficult, however.
So study researcher Michael Hren,
a professor of chemistry and geosciences at the University of
Connecticut, and his colleagues turned to snails. They tested fossils of
a freshwater snail, Viviparus lentus, from the Isle of Wight in Great Britain, looking for variations in carbon and oxygen molecules called isotopes. [Gallery: Strange & Slimy Snails]
Most important, the researchers examined how the carbon and oxygen
isotopes were bound together in the fossils. These bonds are
temperature-dependent, so they told researchers how chilly or warm the
water was when the snails lived. From that information, the scientists
could calculate how hot the air must have been.The shells revealed that freshwater temperatures cooled by 18 degrees F (10 degrees C) during the Eocene-Oligocene transition. The water-cooling translates to about a 7.2 degree to 11 degree F (4 to 6 degrees C) drop in air temperatures over northern Europe, the scientists reported.
These findings are important because human greenhouse gas emissions could drive atmospheric carbon dioxide
up to near-Eocene levels. Ice cores put pre-industrial carbon dioxide
levels at about 278 parts per million from A.D. 1000 to A.D. 1800.
Today, atmospheric carbon dioxide levels are at about 397 parts per
million and climbing. According to a 2011 study in the journal Science
by researchers at the National Center for Atmospheric Research (NCAR), if carbon dioxide continues to rise as it is today, Earth's atmosphere could hit 900 to 1,000 parts per million of carbon dioxide by 2100.
"We are on a path to fundamentally alter our global climate state,"
Hren said in a statement. "These data definitely give you pause."end quote from:
http://news.yahoo.com/ancient-snail-shells-hint-future-global-warming-191044808.html
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