The Hot Zone

Tens of thousands of years needed for Earth to recover from mass carbon releases

Posted by Alison Hawkes on December 1, 2010
Category : Climates of the Past

It’s easy to come up with ways that carbon is released into the atmosphere — an erupting volcano, a massive wildfire, or in today’s world, millions of fossil fuel burning cars and power plants. But how does carbon eventually get put back into the earth?

A paper published in Nature Geoscience this month by scientists at Purdue University and the University of California at Santa Cruz examined the Palaeocene-Eocene Thermal Maximum, a 170,000 year period of global warming that took place 56 million years ago. It was caused by a single event that released the equivalent of burning the entire reserve of present day fossil fuels.

Obviously in the 56 million years since then, the carbon has settled out. But how long that took is a question that has puzzled scientists and has obvious relevance to climate change concerns today. The good news, according to the study in Geoscience, is that the rate of recovery is much more rapid than expected when you take into account the absorptive abilities of the biosphere and Earth’s crust. Don’t get too excited. They’re talking 30,000 to 40,000 years — long past the future generations within our site.

What made the difference was the regrowth of vegetation and living organisms after the catastrophe, which do a great job of storing carbon, and ocean removal of atmospheric CO2. The oceans would have become supersaturated with carbon compounds, resulting in much of it settling onto the seafloor as carbonate deposits, which have been observed in seafloor records.

What’s still not known is what triggered the onset of carbon sequestration. And, of course, tens of thousands of years is a long time to wait for that to happen, no matter how rapid that is on a geologic timescale.

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