The Hot Zone

Past warming one-tenth rate of modern day climate change

Posted by Alison Hawkes on June 6, 2011
Category : Climates of the Past

Climate scientists find it useful to use analogs to put modern day change into historical perspective. No analog is more useful than the Palaeocene–Eocene Thermal Maximum, a period of rapid warming that occurred 56 million years ago when the continents were virtually in the same location as today.

During the PETM, temperatures shot up 9 to 16 degrees Fahrenheit over a period of 20,000 years, a result of a massive release of carbon into the ocean and atmosphere.

A new study out of Penn State University finds that carbon is now being released into the atmosphere at a rate 10 times as fast. The results, published in the current online edition of the journal Nature Geoscience, suggests major implications for today’s warming world. The PETM brought on ocean acidification, which likely caused a major disruptions to ecosystems, including the widespread extinction of waterborne foraminifera, tiny single-celled organisms with distinctive shells. What does today’s rate of climate change mean for species?

“Rather than the 20,000 years of the PETM which is long enough for ecological systems to adapt, carbon is now being released into the atmosphere at a rate 10 times faster,” said lead researcher Lee Kump, as quoted in a Penn State press release. “It is possible that this is faster than ecosystems can adapt.”

The data comes from sediment cores off the polar island Spitsbergen. The researchers felt that the shallow water mud cores would be more accurate than previously studied deep sea samples. The accuracy of those deep sea samples, based on layers of calcium carbonate in shelled marine life, may have been degraded by the ocean acidity.

The mud sample results were run through a climate model to estimate the rate of temperature change during the PETM over time. The result – an average of 0.0125 degrees every 1,000 years – is far below the kind of change we’re observing today.

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