Expansion of forests in the European Arctic could result in the release of carbon dioxide

[DavidDvorkin]

Carbon stored in Arctic tundra could be released into the atmosphere by new trees growing in the warmer region, exacerbating climate change, scientists have revealed.

The Arctic is getting greener as plant growth increases in response to a warmer climate. This greater plant growth means more carbon is stored in the increasing biomass, so it was previously thought the greening would result in more carbon dioxide being taken up from the atmosphere, thus helping to reduce the rate of global warming.

However, research published in Nature Climate Change, shows that, by stimulating decomposition rates in soils, the expansion of forest into tundra in arctic Sweden could result in the release of carbon dioxide to the atmosphere.

http://www.eurekalert.org/pub_releases/2012-06/uoe-eof061512.php

We are still further screwed.

[waddirum]

1. this is frightening enough

but what has me really shitting my pants is the bubbling up of arctic methane from the sea. CH4 has a significantly greater effect on climate change than CO2.

[DavidDvorkin]

2. And that could have a catastrophically sudden effect.

[muriel_volestrangler]

3. There's a new paper on that; it's thought it affects long term temperatures more

The methane emission fluxes are higher than previous estimates, but that’s not really the most important point, because emissions from the Arctic are small relative to low-latitude wetlands, and doubling or even nearly quadrupling the Arctic fluxes (in one of their analyzed regions), they would still be small in terms of global climate forcing. And the lifetime of methane in the atmosphere is short, about 10 years, so methane doesn’t build up like CO2, SF6, and to a lesser extent N2O do.

The really interesting take-away from the new paper is how it shows that the near-surface geology and freezing state conspire to control the venting of accumulated gas dribbling up from below, and the decompostion of frozen soil carbon. They have so many methane seep observations that they are able to correlate them with (1) currently melting permafrost, which allow fossil soil carbon deposits from the last ice age called Yedoma to decompose (Zimov et al 2006) and (2) melting ice sheets and glaciers “un-crunching” the landscape as they fade away, making cracks that vent methane from deep thermal sources. Glaciers that melted long ago no longer vent methane, showing that the methane is transiently venting from built-up pools of gas.

What these results do not do is fundamentally change the game, in my opinion. We can now see more clearly that most of the methane flux from the Arctic today are of types of emission that will respond to climate warming. But the general response time of the system is slow, decades to centuries, rather than potentially poised to release a huge pulse of methane within a few years. Earthquakes and submarine landslides are sudden events, but small individually in terms of potential methane release. The new data do not change that. Walter Anthony et al. compare an estimate the amount of methane in the Arctic, 1200 Gton C, with the 5 Gton C of methane in the atmosphere. That’s the nightmare comparison, but it’s only really relevant if the methane comes out all at once. (The Arctic estimate is for methane itself and is mostly methane hydrate, but keep in mind that there is also a comparable amount of decomposable soil carbon.)

In my opinion, the largest impact of all this methane will probably be to the long-term future evolution of climate. Avoiding a peak warming of 2 degrees C or more requires keeping the total emission of carbon down to less than about 1000 Gton C (Allen et al 2009). We have already burned about 300 Gton C, and cut 200 Gton C although the land surface has taken up enough carbon to achieve net wash. So maybe we’re 1/3 of the way there, say 700 Gton C left to go. The 1200 Gton C of Arctic methane hydrates and the permafrost carbon stack up pretty menacingly against our 700 Gton left to go, and the comparison is relevant even if the carbon is emitted slowly, or as CO2 rather than methane, or even if it is released into the ocean rather than into the air (it will still equilibrate with the atmosphere, after a few centuries, converging to the same “long tail” CO2 trajectory that would have resulted from atmospheric release).

http://www.realclimate.org/index.php/archives/2012/06/methane-game-upgrade/#more-12179