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The Temperature Sensitivity of Global Biospheric Respiration
Mahecha, M.D., Reichstein, M., Varvalhais, N., Lasslop, G., Lange, H., Seneviratne, S.I., Vargas, R., Ammann, C., Arain, M.A., Cescatti, A., Janssens, I.A., Migliavacca, M., Montagnani, L. and Richardson, A.D. 2010. Global convergence in the temperature sensitivity of respiration at ecosystem level. Science 329: 838-840.

The fourteen authors of this impressive new analysis write that "the respiratory release of carbon dioxide from the land surface is a major flux in the global carbon cycle," and that "understanding the sensitivity of respiratory processes to temperature is central for quantifying the climate-carbon cycle feedback."

What was done
In condensing their explanation of a complex set of operations to but a few words, Mahecha et al. say they "approximated the sensitivity of terrestrial ecosystem respiration to air temperature (Q10) across 60 FLUXNET sites with the use of a methodology that circumvents confounding effects."

What was learned
The international team of scientists, hailing from Belgium, Canada, Germany, Italy, Norway, Portugal, Switzerland and the United States, says their results "may partly explain recent findings indicating a less pronounced climate-carbon cycle sensitivity (Frank et al., 2010) than assumed by current climate-carbon cycle model parameterizations." Indeed, and "contrary to previous findings," as they describe it, they say their results "suggest that Q10 is independent of mean annual temperature, does not differ among biomes, and is confined to values around 1.4 ± 0.1"

What it means
Perhaps the most significant consequence of the new assessment of the issue was articulated by Reich (2010) in a Perspective article in Science that discusses Mahecha et al.'s findings, wherein he writes that their new work "reduces fears that respiration fluxes may increase strongly with temperature, accelerating climate change." Thus, this long-held climate-alarmist tenet no longer appears to have much support within the community of global-change scientists.

Frank, D.C., Esper, J., Raible, C.C., Büntgen, U., Trouet, V., Stocker, B. and Joos, F. 2010. Ensemble reconstruction constraints on the global carbon cycle sensitivity to climate. Nature 463: 527-530.

Reich, P.B. 2010. The carbon dioxide exchange. Science 329: 774-775.

Reviewed 1 September 2010