Wednesday, June 13, 2012

Forest soil carbon release a vicious Global Warming feedback loop say researchers

Global warming is likely to accelerate release of forest soil carbon say researchers. This is another climate feedback loop. Rising temperatures are likely to accelerate forest soil carbon decomposition leading to more CO2 released into the atmosphere, compounding global warming. Rather than these forests acting as a carbon sink, warmer temperatures may make them a major source of greenhouse gas emissions further contributing to global warming warn the researchers.

"Our results suggest that large stores of carbon that built up over the last century as forests recovered will erode with rising temperatures," said Susan Trumbore of the Max Planck Institute for Biogeochemistry and University of California at Irvine (UCI), who led the research team.

There are vast stores of carbon in forest soils. This new research was conducted in the woodlands of Wisconsin and North Carolina, with soils being heated increasing the release of carbon dioxide up to eight times. This has demonstrated the vulnerability of carbon presently locked in topsoil to increasing temperatures in a warming world.

Global climate carbon-cycle models account for the acceleration of release of soil carbon to the atmosphere with warming, but the size of the feedback is largely unknown. This research paper - Warming accelerates decomposition of decades-old carbon in forest soils published in PNAS highlights the vulnerability of soil carbon in forests to warming.

"We found that decades-old carbon in surface soils is released to the atmosphere faster when temperatures become warmer," said lead author Francesca Hopkins, a doctoral researcher in UCI's Earth system science department. "This suggests that soils could accelerate global warming through a vicious cycle in which man-made warming releases carbon from soils to the atmosphere, which, in turn, would warm the planet more."

Although the research was conducted in the USA, the soil carbon content of all forested lands should be seen as vulnerable.

Doctoral student Francesca Hopkins said "These are carbon dioxide sources that, in effect, we can't control. We could control how much gasoline we burn, how much coal we burn, but we don't have control over how much carbon the soil will release once this gets going."