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Penn State study ties high volcanic CO2 release to prehistoric climate change
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Prehistoric evidence offers proof that high carbon dioxide levels in the atmosphere cause global warming.
High carbon-dioxide levels in Earth's atmosphere 55.9 million years ago caused average temperatures to increase by 9 to 16 degrees Fahrenheit, a Penn State University study concludes.
That means fossil-fuel burning that's filling the atmosphere with high levels of carbon dioxide could raise temperatures dramatically in a process already under way.
In the study published in Nature Geoscience, Lee R. Kump, Penn State professor of geosciences, said Norwegian core samples reveal that volcanic activity that burned accumulated carbon-based materials 55.9 million years ago increased the rate of carbon emissions into the atmosphere by a factor of about 100 over background volcanic rates.
Those elevated rates of carbon emissions generated during the first 20,000 years of the Paleocene-Eocene Thermal Maximum -- a warming event that lasted 170,000 years -- represent one-tenth of the rate of fossil-fuel combustion that's occurring today. Yet the rising temperatures at that time sent species on mass migrations in search of cooler regions, with evidence that 3 million years later crocodiles were living in the polar regions, Mr. Kump said.
The bit of good news from the PETM is that plants, animals and oceans had 20,000 years to adapt to severe climate change.
The bad news?
Climate change is occurring so quickly nowadays -- in decades and centuries rather than millennia -- that people, animals, plants and oceans have little time to adjust to rising temperatures, portending extinctions, destruction of ocean life and major challenges for humankind, Mr. Kump said.
For example, excess carbon dioxide in the atmosphere increases the acidity of the oceans, posing survival problems for plankton, coral reefs and ocean life. As temperatures climb, drier areas will get drier, Mr. Kump said, while wet areas will get even wetter.
The study, he said, provides a stark warning that continued burning of 9 gigatons of carbon-based fuels each year (or about 10 billion tons) in the form of fossils fuels represents 10 times the rate of carbon-dioxide production that occurred during the PETM.
During global history, the annual rate of carbon-dioxide emissions to the atmosphere was about 0.06 gigatons. During the PETM, the average annual rate grew to a gigaton, with a peak of 1.7 gigatons. That level was much less than modern emissions.
What happened 55.9 million years ago "is thought to be the best ancient analogue for future climate change caused by fossil fuel burning," Mr. Kump said.
Typically, such studies have involved shallow core drilling in areas that were deep ocean bottom 55.9 million years ago. But that evidence usually has been adversely affected or destroyed by the high acidity of ocean water during the PETM.
But during a World Universities Network expedition to Spitsbergen, Norway, researchers and graduate students discovered a supply of rock cores curated by "a forward-thinking young coal-mining company geologist, Malte Jochmann."
While deep-sea cores usually have from 4 inches to 3 feet that correspond to the PETM, Mr. Kump said, the Spitsbergen cores provided 150 meters, or almost 500 feet, of sediment from the PETM.
Those core samples included mud from shallow oceans that contain organic matter, which supplied the carbon isotope necessary for researchers to calculate greenhouse-gas levels of the atmosphere during that ancient era.
"We went to a place where the tape recorder was still playing and playing with high fidelity," he said of the Norwegian core samples from the PETM era.
Calculations of greenhouse-gas levels, based on carbon-isotope ratios in core samples through the first 20,000 years of the PETM, provided evidence of the atmospheric temperatures at that time.
"The outcome was a warming of from 9 to 16 degrees Fahrenheit and an acidification event in the oceans," Mr. Kump said. "Rather than the 20,000 years of one PETM, which is long enough for ecological systems to adapt, carbon is now being released into the atmosphere at a rate 10 times faster. It is possible that this is faster than ecosystems can adapt.
"Every time we look at Earth history and see evidence of carbon dioxide, we see warming," he said. "We see it again here. Our study, like others, documents clearly the consequences of the buildup of carbon dioxide from fossil fuels, and that consequence is warming."
But the buildup of carbon dioxide during the PETM occurred slowly.
The buildup of carbon dioxide in the atmosphere today, he said, could pose major impacts for people and all of life.
"What we're facing may be unprecedented," he said.
Jeffrey T. Kiehl, who heads the Climate Modeling Section at the National Center for Atmospheric Research, among other positions, said the Kump study provides context for future studies of climate change.
"Studies of warm past climates provide background understanding for our present warming world," he said. "Much emphasis has been placed on the magnitude of change which will take place in the future and this is certainly important. What this study provides is a perspective on the rate of change of injection of carbon dioxide into the atmosphere.
He said the release of carbon dioxide into the atmosphere 55.9 million years ago occurred at a much slower rate than what's occurring now with the burning of fossil fuels.
"This is an important message for people to understand," he said. "Why? Because species -- including humans -- will need to respond to the rapid change in climate associated with the increase in the greenhouse gas, carbon dioxide."
First Published June 16, 2011 12:00 am
