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Earth's Changing Biosphere

Reference
Fung, I. 2013. A hyperventilating biosphere. Science 341: 1075-1076.
Recently, Graven et al. (2013), "in a masterful stroke," in the words of Inez Fung (2013), "stitched together separate pieces of aircraft CO2 records over the North Pacific" to evaluate recent trends in the annual amplitude of the atmosphere's CO2 concentration in the middle troposphere, about 3 to 6 km above the Earth's surface, which were driven primarily by the aerial fertilization effect of the regularly-recurring yearly increases in the atmosphere's CO2 content, as well as by high-latitude warming. Writing in a "Perspective" on this Report in Science, Fung summarizes Graven et al.'s findings and makes some comments on them.

According to Fung, "the 50-year amplitude trends in the mid-troposphere resemble those at the few monitoring sites at the surface," noting that "the trends are huge: ~10% per decade at high latitudes and ~5% per decade over the mid-latitudes." As for what has been causing these huge increases, Fung states that "enhanced photosynthesis alone is not enough to explain the large increase in CO2 amplitude seen by Graven et al.," and she indicates that the fourteen researchers also implicate "northward migration of the tree line, increased shrub cover in the Arctic, and reestablishment of forests after fires have enhanced carbon uptake to the extent necessary to explain the amplitude trend," along with the concurrent increase in temperature that has helped to promote some of these other phenomena.

In short, Fung states that "the biosphere is changing, and changing rapidly." And "currently," she notes, "it is a sink for a quarter of the anthropogenic CO2 emissions." But will it continue? Only time will tell. But as things stand today, she remarks that "surely, the biosphere must be enjoying the warming."

Additional References
Graven, H.D., Keeling, R.F., Piper, S.C., Patra, P.K., Stephens, B.B., Wofsy, S.C., Welp, L.R., Sweeney, C., Tans, P.P., Kelley, J.J., Daube, B.C., Kort, E.A., Santoni, G.W. and Bent, J.D. 2013. Enhanced seasonal exchange of CO2 by northern ecosystems since 1960. Science 341: 1085-1089.

Archived 11 December 2013