Global warming: Permafrost melt suspected as cause of extreme global warming ... - Summit County Citizens Voice

This is thawing permafrost on the North Slope along the Sagavanirktok River near Deadhorse, Alaska. PHOTO COURTESY KEVIN SCHAEFER/NSIDC.

Researchers pinpoint links between Earth’s orbit, carbon cycle and temperatures

By Summit Voice

SUMMIT COUNTY â€" Instead of massive releases of carbon from ocean sources, melting tundra may have been the fuel for a series of extreme global warming events about 55 million years ago, according to University of Massachusetts Amherst climate researcher Rob DeConto.

Reporting his tean’s findings in Nature, DeConto said his modeling shows a simple new mechanism to explain the rapid warming during the Paleocene-Eocene Thermal Maximum, and a sequence of similar, smaller warming events afterward.

“The standard hypothesis has been that the source of carbon was in the ocean, in the form of frozen methane gas in ocean-floor sediments,” DeConto said. “We are instead ascribing the carbon source to the continents, in polar latitudes where permafrost can store massive amounts of carbon that can be released as CO₂ when the permafrost thaws.”

The new view is supported by calculations estimating interactions of variables such as greenhouse gas levels, changes in the Earth’s tilt and orbit, ancient distributions of vegetation, and carbon stored in rocks and in frozen soil.

While the amounts of carbon involved in the ancient soil-thaw scenarios was likely much greater than today, implications of the study appear dire for the long-term future as polar permafrost carbon deposits have begun to thaw due to burning fossil-fuels, DeConto said.

“Similar dynamics are at play today. Global warming is degrading permafrost in the north polar regions, thawing frozen organic matter, which will decay to release CO₂ and methane into the atmosphere. This will only exacerbate future warming in a positive feedback loop.”

He and colleagues at Yale, the University of Colorado, Penn State, the University of Urbino, Italy, and the University of Sheffield, U.K., designed an accurate model ― elusive up to now ― to satisfactorily account for the source, magnitude and timing of carbon release at the PETM and subsequent very warm periods, which now appear to have been triggered by changes in the Earth’s orbit.

Earth’s atmospheric temperature is a result of energy input from the sun minus what escapes back to space. Carbon dioxide in the atmosphere absorbs and traps heat that would otherwise return to space.

The PETM was accompanied by a massive carbon input to the atmosphere, with ocean acidification, and was characterized by a global temperature rise of about 5 degrees Celsius in a few thousand years. Until now, it has been difficult to account for the massive amounts of carbon required to cause such dramatic global warming events.

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Filed under: climate and weather, Environment, global warming Tagged: | climate, Environment, global warming, Paleoceneâ€"Eocene Thermal Maximum, permafrost meltdown, University of Massachusetts Amherst