Recently, some poor reporting of a new study has set the blogosphere aflutter about “lower sensitivity” of the climate to greenhouse gases.
Joe Romm at Climateprogress has a great analysis of what the study says and doesn’t say. One of the key pieces of the puzzle – the new research, by Schmittner et al, summarizes the warming effect of “fast” climate feedbacks, like sea ice and water vapor, but leaves out the slower, longer term feedbacks like tundra melt, and the accompanying methane release. ( see the video above – methane is a greenhouse gas much more powerful than CO2)
Now, news from the University of Alaska Fairbanks underlines the dangers of ignoring the “slow” feedbacks, which may not be so slow, after all…
FAIRBANKS — An international group of researchers believes greenhouse gases from thawing permafrost will be released at a much faster rate than previously estimated, which could have significant implications for climate change projections.
A survey of 41 scientists — including seven University of Alaska Fairbanks researchers — estimates the amount of carbon released from thawing permafrost by 2100 will be 1.7 to 5.2 times larger than previously estimated. Their conclusions, reported Wednesday in the scientific journal Nature, describe permafrost thawing as a likely accelerator of global warming.
“Our collective estimate is that carbon will be released more quickly than models suggest, and at levels that are cause for serious concern,” the article states.
The higher figures come about because of an ongoing reevaluation of the carbon stored in permafrost.
In most soils such material is typically in the top several feet, but in frozen soils those carbon-filled sediments can be much deeper.
Because of that, the estimated amount of carbon stored in northern soils has tripled in recent years, to roughly 1,700 billion tons. That’s four times more than all the carbon emitted by human activity since the Industrial Revolution and twice as much as is currently present in the atmosphere.
And the picture is even more alarming for the end of the century. The scientists calculate that about than 300 billion metric tons of carbon will belch from the thawing Earth from now until 2100.
Adding in that gas means that warming would happen “20 to 30 percent faster than from fossil fuel emissions alone,” said Edward Schuur of the University of Florida. “You are significantly speeding things up by releasing this carbon.”
Usually the first few to several inches of permafrost thaw in the summer, but scientists are now looking at up to 10 feet of soft unfrozen ground because of warmer temperatures, he said. The gases come from decaying plants that have been stuck below frozen ground for millennia.