Carbon-Belching Microbes Pose Yet Another Global Warming Feedback Loop

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Perhaps the most frightening thing about climate change is that we don't have a great idea about exactly how fast it's going to get really frightening—if global warming activates any number of known feedback loops, temperatures could spiral out of control faster than our models currently predict.

Scientists are particularly concerned about the thawing permafrost and releasing the methane trapped within (the gas would trap more heat in the atmosphere and provoke more warming) and losing the Arctic sea ice that reflects sunlight back into space (as that ice surface dwindles, more heat is absorbed in the ocean, melting more ice). There are many others, and each presents an unknown boundary that could throw a wrench into a system that's already going haywire—think of them as a collection of invisible trip wires that would screw everything over.

NASA just uncovered another one—melting sea ice releases methane—and here comes yet another. The New York Times reports:

Now scientists have identified another feedback loop that may be accelerating the loss of carbon dioxide from the topsoil of forests in the United States, contributing to climate change ... the warmer it gets, the more active are the microbes that eat the topsoil and exhale carbon dioxide afterward.

While that finding is not surprising, said the lead author, Francesca Hopkins, a doctoral researcher in the Department of Earth System Science at Irvine, she and her collaborators also found that in warmer temperatures the microbes are better able to digest decades-old carbon stored in the soils. Scientists had previously that the old carbon was inaccessible because it had become fixed in the soil.

Essentially, the warmer it gets, the easier time microbes will have devouring carbon in forests' topsoil; even the stuff previously thought inedible. And as the microbes belch out more and more carbon, the warmer it will get.

This could have some serious ramifications. "Under the moderate warming scenario predicted by the Intergovernmental Panel on Climate Change," notes the Times, "Ms. Hopkins’s experiment indicated that the respiration rates of the microbes — and the amount of carbon-dioxide they exhale — would roughly double by 2100." Which, of course, would significantly speed up warming worldwide. The bottom line is, shiiiiiiiiit.

Tags: Global Climate Change | Global Warming Effects