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Here is a news release from the US Geological Survey.
I've copied some parts of it, but please read the entire release before commenting.
http://www.usgs.gov/newsroom/article_pf.asp?ID=2326
In brief, there are lots of uncertainties and potentials for climate change to impact
the role of the arctic as a CO2 sink and CH4 source. The science isn't there yet
to make much of a prediction and it may be decades before we know for sure.
However, what is interesting are the current CO2 sink and CH4 source numbers.
Although the CH4 source is one eighth the CO2 sink (50 vs 400), since CH4 is 23 times
more powerful as a greenhouse gas, the implication is that the Arctic is
already providing a positive feedback to climate change. It is providing roughly
effectively 3 times more greenhouse gases than it is absorbing. In other
words, even if human CO2 emissions were reduced to near zero, there would
still be a net positive global warming from sources/sinks inherit in the Arctic.
If true, that's a huge statement because unless there are significant changes in the
dynamics of the Arctic, that means climate change is probably irreversible.
By irreversible, I mean even if Humans were to cease all CO2 emissions
(which is highly unlikely), there would still be climate change due to the current
CH4 emissions from the Arctic.
I've copied some parts of it, but please read the entire release before commenting.
http://www.usgs.gov/newsroom/article_pf.asp?ID=2326
In brief, there are lots of uncertainties and potentials for climate change to impact
the role of the arctic as a CO2 sink and CH4 source. The science isn't there yet
to make much of a prediction and it may be decades before we know for sure.
However, what is interesting are the current CO2 sink and CH4 source numbers.
Although the CH4 source is one eighth the CO2 sink (50 vs 400), since CH4 is 23 times
more powerful as a greenhouse gas, the implication is that the Arctic is
already providing a positive feedback to climate change. It is providing roughly
effectively 3 times more greenhouse gases than it is absorbing. In other
words, even if human CO2 emissions were reduced to near zero, there would
still be a net positive global warming from sources/sinks inherit in the Arctic.
If true, that's a huge statement because unless there are significant changes in the
dynamics of the Arctic, that means climate change is probably irreversible.
By irreversible, I mean even if Humans were to cease all CO2 emissions
(which is highly unlikely), there would still be climate change due to the current
CH4 emissions from the Arctic.
Carbon generally enters the oceans and land masses of the Arctic from the atmosphere and largely accumulates in permafrost, the frozen layer of soil underneath the land’s surface. Unlike active soils, permafrost does not decompose its carbon; thus, the carbon becomes trapped in the frozen soil. Cold conditions at the surface have also slowed the rate of organic matter decomposition, McGuire says, allowing Arctic carbon accumulation to exceed its release.
But recent warming trends could change this balance. Warmer temperatures can accelerate the rate of surface organic matter decomposition, releasing more carbon dioxide into the atmosphere. Of greater concern, says McGuire, is that the permafrost has begun to thaw, exposing previously frozen soil to decomposition and erosion. These changes could reverse the historical role of the Arctic as a sink for carbon dioxide.
“In the short term, warming temperatures could release more Arctic carbon to the atmosphere,” says McGuire. “And with permafrost thawing, there will be more available carbon to release.”
On the scale of a few decades, the thawing permafrost could also result in a more waterlogged Arctic, says McGuire, a situation that could encourage the activity of methane-producing organisms. Currently, the Arctic is a substantial source of methane to the atmosphere: as much as 50 million metric tons of methane are released per year, in comparison to the 400 million metric tons of carbon dioxide the Arctic stores yearly. But methane is a very potent greenhouse gas – about 23 times more effective at trapping heat than carbon dioxide on a 100-year time scale. If the release of Arctic methane accelerates, global warming could increase at much faster rates.
“We don’t understand methane very well, and its releases to the atmosphere are more episodic than the exchanges of carbon dioxide with the atmosphere,” says McGuire. “It’s important to pay attention to methane dynamics because of methane’s substantial potential to accelerate global warming.”
But uncertainties still abound about the response of the Arctic system to climate change. For example, the authors write, global warming may produce longer growing seasons that promote plant photosynthesis, which removes carbon dioxide from the atmosphere. Also, the expansion of shrubs in tundra and the movement of treeline northward could sequester more carbon in vegetation. However, increasingly dry conditions may counteract and overcome these effects. Similarly, dry conditions can lead to increased fire prevalence, releasing even more carbon.