Study Shows There's
More CO2 Now Than Past 650K Years
November 25, 2005 — By Lauran Neergaard, Associated Press
WASHINGTON — Scientists are looking
back to a time when "greenhouse gases" were not the problem they are
today, and it is giving them a clearer picture of how people are making
it worse.
A team of European researchers analyzed tiny air bubbles preserved in
Antarctic ice for millennia and determined there is more carbon dioxide
in the atmosphere now than at any point during the last 650,000 years.
The study by the European Project for Ice Coring in Antarctica,
published Friday in the journal Science, promises to spur "dramatically
improved understanding" of climate change, said geosciences specialist
Edward Brook of Oregon State University.
Today, scientists directly measure levels of carbon dioxide and other
greenhouse gases, which accumulate in the atmosphere as a result of
fuel-burning and other processes. Those gases help trap solar heat, like
the greenhouses for which they are named, resulting in a gradual warming
of the planet.
Those measurements are disturbing: Levels of carbon dioxide have climbed
from 280 parts per million two centuries ago to 380 ppm today. Earth's
average temperature, meanwhile, increased about 1 degree Fahrenheit in
recent decades, a relatively rapid rise. Many climate specialists warn
that continued warming could have severe impacts, such as rising sea
levels and changing rainfall patterns.
Skeptics sometimes dismiss the rise in greenhouse gases as part of a
naturally fluctuating cycle. The new study provides ever-more definitive
evidence countering that view, however.
Deep Antarctic ice encases tiny air bubbles formed when snowflakes fell
over hundreds of thousands of years. Extracting the air allows a direct
measurement of the atmosphere at past points in time, to determine the
naturally fluctuating range.
A previous ice-core sample had traced greenhouse gases back about
440,000 years. This new sample, from East Antarctica, goes 210,000 years
further back in time.
Today's still rising level of carbon dioxide already is 27 percent
higher than its peak during all those millennia, said lead researcher
Thomas Stocker of the University of Bern, Switzerland.
"We are out of that natural range today," he said.
Moreover, that rise is occurring at a speed that "is over a factor of a
hundred faster than anything we are seeing in the natural cycles,"
Stocker added. "It puts the present changes in context."
The team, which included scientists from France and Germany, found
similar results for methane, another greenhouse gas.
Researchers also compared the gas levels to the Antarctic temperature
over that time period, covering eight cycles of alternating glacial or
ice ages and warm periods. They found a stable pattern: Lower levels of
gases during cold periods and higher levels during warm periods.
The bottom line: "There's no natural condition that we know about in a
really long time where the greenhouse gas levels were anywhere near what
they are now. And these studies tell us that there's a strong
relationship between temperature and greenhouse gases," said Oregon
State's Brook. "Which logically leads you to the conclusion that maybe
we should worry about temperature change in the future."
A lengthening history of greenhouse gas concentrations should help
climate specialists build better models about what the future might
bring, Stocker said. It also may help answer additional questions such
as how long ago humans started influencing greenhouse gas accumulations,
and what impact other factors such as ocean currents play in the
complexities of climate change.
Just a decade ago, scientists weren't sure it was possible to trace
greenhouse gas concentrations back so far in ice. Now, Brook is part of
another international research team preparing to hunt an ice-core sample
dating back a million years or more, hoping to reach eras when Earth's
temperature was significantly warmer.
Source: Associated Press
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