Claim: Climate warming accelerating carbon loss from thawing Arctic soils

What ‘accelerating’ warming?

The media release is below.

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Climate warming accelerating carbon loss from thawing Arctic soils, Dartmouth study finds
DARTMOUTH COLLEGE

HANOVER, N.H. – Warmer, wetter conditions in the Arctic are accelerating the loss of carbon stored in tundra and permafrost soils, creating a potential positive feedback that further boosts global temperatures, a Dartmouth College study finds.

The findings appear in the journal Climate Change Responses.

For thousands of years, Arctic grasses, shrubs and other plants have removed carbon from the atmosphere and stored it in the tundra soil, where microbes feed on decomposing organic matter. Now, shrub expansion is transforming the tundra landscape, but its impact on carbon stored in high-latitude soils is poorly understood. Arctic soils contain half of global soil carbon and more than twice the amount of carbon as the entire atmosphere. Soil carbon decomposition, which is temperature sensitive, is a potentially important source of greenhouse gases, which could create a positive feedback to global climate change through the release of greenhouse gases from decomposing organic matter. This soil carbon feedback could transform the Arctic tundra from a carbon sink to a carbon source.

To understand the complex relationship that determines the fate of soil carbon, the Dartmouth researchers collected soil from shrub and grass vegetation in western Greenland and conducted controlled experiments back in the laboratory. They measured carbon dioxide emissions from mineral soils of the two vegetation types incubated at five temperatures and two moisture levels. They found that soil in grassy areas had greater carbon storage, greater carbon losses from decomposition and a higher temperature sensitivity of decomposition than shrub soils. The results suggest that soil respiration and organic carbon decomposition in the tundra, especially in grassy areas, will increase with warming temperatures and rising soil moisture, resulting in increased carbon dioxide emissions to the atmosphere.

“Our results highlight the importance of the interactive effects of vegetation type, temperature and moisture in determining of the response of soil decomposition to climate change,” says lead author Julia Bradley-Cook, who conducted the study as part of her doctorate in Ecology and Evolutionary Biology at Dartmouth and who is now a Congressional Science Fellow. “Any soil moisture increases consistent with climate model projections are expected to increase soil respiration in both vegetation types. Also, higher soil moisture should increase the temperature sensitivity of grassy soils but may have little to no effect on shrub soils. Shrub expansion into grassy areas could reduce soil carbon accumulation and the temperature sensitivity of carbon mineralization, such that these soils would more closely resemble the carbon storage and temperature sensitivity of shrub soil.”

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5 thoughts on “Claim: Climate warming accelerating carbon loss from thawing Arctic soils”

  1. Geoff … the rate of Arctic warming over the last 100 years . ? .. how pray tell were the Arctic temps measured across the entire Arctic 100 – 90 – 80 – 70 – 60 years ago ? short answer … they weren’t … so fail … and how many points of Arctic measurement are there even today ? short answer – less than a dozen for the entire Arctic … so garbage in garbage out

  2. oh and we are still well below the supposed Arctic temperatures from the 1930’s … nice cherry pick of a starting point 1981 …

  3. “how many points of Arctic measurement are there even today”

    The link you are trying to critique provides information about the source of measurement, which you could read:

    “The surface temperature records from 1981 to 2001 were based on thermal infrared data from the Advanced Very High Resolution Radiometer (AVHRR) onboard NOAA satellites. The AVHRR sensor detects radiation in the visible and thermal infrared range of the electromagnetic spectrum. These satellite temperature data were compared with accurate ground-based data taken during the one-year-long Arctic ice station project called the Surface Heat Budget in the Arctic (SHEBA) from 1997 to 1998. Comiso found that the two datasets are extremely consistent with each other.

    “This study is unique in that previously, similar studies made use of data from very few points scattered in various parts of the Arctic region,” says Comiso. “These results show the large regional and seasonal differences in the trends that only satellite data can provide.” ”

    Obviously, your claim that NASA does not know enough about past arctic temperatures to make a statement about rate of warming conflicts with your confident claim that we are still “well below” the arctic temperatures from the 1930s. I am happy to see / learn about your source for this claim, presumably showing current arctic temperatures many tenths of a degree cooler than the 30s. Tamino surveyed the main data sets here and writes:

    “Using the GISS LOTI (land+ocean temperature index), the answer is “No.” Using the GISS met-station data, the answer is “No.” Using the HadCRUT4 (land+ocean) data, the answer is “No.” Using the CRUTEM4 (land only) data, the answer is “No.” Using the NCDC land+ocean data, the answer is “No.” Using the NCDC land-only data, the answer is “No.” Using the Berekely data, the answer is “No.” … All those “No” answers aren’t close calls.”

    E.g. here is the BE data plot:

    https://tamino.files.wordpress.com/2014/01/berk2.jpeg

  4. Excuse me, won’t a “warmer” arctic allow more plant growth, said growth only possible by CONSUMING CO2? Or did the laws of biology get thrown out by the AGW religion?

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