Thursday, May 16, 2013

Thermogeddon Averted, Redux

One of the doom scenarios posited by Catastrophic Anthropogenic Warming (CAGW) proponents has been the theory that warmer climates would cause loss of soil carbon from the massive amounts of "fossil" carbon in northern regions, particularly peat field, where the cold temperatures inhibit the bacterial decay that would release the stored carbon as CO2.  The hypothesis was that higher temperature would cause faster degradation and CO2 and methane release, leading to more warming and more release, in a positive feed back loop of runaway greenhouse effect, resulting in much higher CO2 and methane concentrations in the atmosphere and higher temperatures.

Then somebody did the experiment:

Long-term warming restructures Arctic tundra without changing net soil carbon storage
High latitudes contain nearly half of global soil carbon, prompting interest in understanding how the Arctic terrestrial carbon balance will respond to rising temperatures. Low temperatures suppress the activity of soil biota, retarding decomposition and nitrogen release, which limits plant and microbial growth. Warming initially accelerates decomposition, increasing nitrogen availability, productivity and woody-plant dominance. However, these responses may be transitory, because coupled abiotic–biotic feedback loops that alter soil-temperature dynamics and change the structure and activity of soil communities, can develop. Here we report the results of a two-decade summer warming experiment in an Alaskan tundra ecosystem. Warming increased plant biomass and woody dominance, indirectly increased winter soil temperature, homogenized the soil trophic structure across horizons and suppressed surface-soil-decomposer activity, but did not change total soil carbon or nitrogen stocks, thereby increasing net ecosystem carbon storage. Notably, the strongest effects were in the mineral horizon, where warming increased decomposer activity and carbon stock: a ‘biotic awakening’ at depth.
In retrospect, this makes sense in that all that "fossil" carbon in the arctic soils was likely laid down at higher temperatures, probably the Holocene Climate Optimum.

Found at Watts Up With That, of course.

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