Somewhat in the shadow of the big state-of-the-Arctic publication today is a related paper in Nature, an expert elicitation on the risks of methane releases from permafrost thaw by Schuur and Abbott is released today.
Climate change: High risk of permafrost thaw
- Nature 480, 32–33 (01 December 2011)
Experts were fairly tightly clustered in their estimates of equivalent CO2 to be expected from this phenomenon. In a high warming scenario, 95% confidence bounds offered CO2 equivalents of:
“30 billion to 63 billion tonnes of carbon by 2040, reaching 232 billion to 380 billion tonnes by 2100 and 549 billion to 865 billion tonnes by 2300”
with roughly 1/3 of those values in a low warming scenario.
The low warming scenario presumably corresponds to the trillion ton scenario, under which we have 450 billion tons left to emit. So at a third of the approximately 300 billion tons by 2100, our safe operating range is substantially cut, from 450 B tons left to about 350 B tons left, with just this one geochemical feedback.
This is not the methane runaway some people lose sleep over, but it’s pretty nasty news just the same. As the paper says:
Knowing how much carbon will be released from the permafrost zone in this century and beyond is crucial for determining the appropriate response. But despite the massive amount of carbon in permafrost soils, emissions from these soils are unlikely to overshadow those from the burning of fossil fuels, which will continue to be the main source of climate forcing. Permafrost carbon release will still be an important amplifier of climate change, however, and is in some ways more problematic: it occurs in remote places, far from human influence, and is dispersed across the landscape. Trapping carbon emissions at the source — as one might do at power plants — is not an option. And once the soils thaw, emissions are likely to continue for decades, or even centuries.
Photo is from the article, captioned “Abrupt thaw, as seen here in Alaska’s Noatak National Preserve, causes the land to collapse, accelerating permafrost degradation and carbon release.”