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Ancient Fossils Show Arctic Now Near Climate Tipping Point

June 30, 2010

From Environment News Service

BOULDER, Colorado, June 29, 2010 (ENS) – Current levels of Earth’s atmospheric carbon dioxide may be high enough to bring about “irreversible” shifts in Arctic ecosystems, according to new research published today by scientists from the United States, Canada and The Netherlands.  

The Arctic climate system is more sensitive to greenhouse warming than previously known said the researchers, who gathered evidence on what is now Ellesmere Island in Canada’s High Arctic from a time period 2.6 to 5.3 million years ago. This period, known as the Pliocene Epoch, occurred shortly before Earth was plunged into an ice age.

“Our findings indicate that CO2 levels of approximately 400 parts per million are sufficient to produce mean annual temperatures in the High Arctic of approximately zero degrees Celsius (32 degrees F),” said lead author Ashley Ballantyne of the University of Colorado at Boulder.

“As temperatures approach zero degrees Celsius, it becomes exceedingly difficult to maintain permanent sea and glacial ice in the Arctic. Thus current levels of CO2 in the atmosphere of approximately 390 parts per million may be approaching a tipping point for irreversible ice-free conditions in the Arctic,” Dr. Ballantyne warned.

The research team points out that the overwhelming majority of climate scientists agree Earth is warming due to increased atmospheric concentrations of heat-trapping gases generated by human activities like fossil fuel burning and deforestation.

Arctic temperatures have risen by about 1.8 degrees F (1 degree C) in the past two decades in response to human-caused greenhouse warming, a trend expected to continue in the coming decades and centuries, said Ballantyne.

Greenhouse gases in the atmosphere have risen from about 280 parts per million during the pre-industrial era on Earth to about 390 parts per million today.

Environmental advocates are calling on governments negotiating the next climate treaty to limit greenhouse gas emissions to 350 parts per million, the level many scientists say will help to avert the worst consequences of climate change.

From Environment News Service

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