The Temperature Sensitivity of Global Biospheric Respiration

Fourteen authors of an impressive new analysis (Mahecha et al., 2010) 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," which is what they then set out to do. In condensing their explanation of a complex set of operations they conducted 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." So what did they find?

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"

In considering their results, perhaps the most significant consequence of the new assessment 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.

Additional References
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.