From Antarctic ice, clues about the effects of greenhouse gases
By Associated Press
Published November 25, 2005
WASHINGTON - There is more carbon dioxide in the atmosphere today than at any point in the past 650,000 years, according to a new study that let scientists peer back in time at greenhouse gases that can help fuel global warming.
By analyzing tiny air bubbles preserved in Antarctic ice for millennia, a team of European researchers highlighted how people are dramatically influencing the buildup of these gases.
The research could spur "dramatically improved understanding" of climate change, said geosciences specialist Edward Brook of Oregon State University.
The study, by the European Project for Ice Coring in Antarctica, is published today in the journal Science.
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, scientists say.
There are some scientists who are skeptical of those theories, however, saying the rise in greenhouse gases is part of a naturally fluctuating cycle.
Deep Antarctic ice encases tiny air bubbles formed when snowflakes fell over hundreds of thousands of years. Extracting the air allows a 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 level of carbon dioxide is 27 percent higher than its peak during all those millennia, said lead researcher Thomas Stocker of the University of Bern in 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 said.
The team, which included scientists from France and Germany, found similar results for methane, another greenhouse gas.
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 could help answer questions such as what impact other factors such as ocean currents play in the complexities of climate change.
