October 10, 2017

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Assessing a New Clue to How Much Carbon Plants Take Up

Tracking the carbonyl sulfide signal could open a new window into the carbon cycle.

The Science

Current climate models disagree on how much carbon dioxide (CO2) land ecosystems take up for photosynthesis. In response, atmospheric scientists, biogeochemists, and oceanographers have proposed measuring a gas called carbonyl sulfide (COS) to help quantify the contribution that photosynthesis makes to carbon uptake.

The Impact

Photosynthesis is a key climate forcing process in the terrestrial biosphere. It removes CO2 from the atmosphere and stores carbon in plants, slowing the rate of climate change. Measurements of atmospheric COS provide the first global-scale estimates of this carbon-climate feedback.


Ten years ago, scientists discovered a massive and persistent biosphere signal in atmospheric COS measurements. In these data, COS and CO2 levels follow a similar seasonal pattern, but the COS signal is much stronger over continental regions, suggesting that the terrestrial biosphere is a sink for COS. The remarkable discovery led scientists to wonder: Could COS be used as a tracer for carbon uptake? An explosive growth in COS studies followed as scientists attempted to answer this question, including a COS record from the present to the Last Glacial Maximum, satellite-based maps of the dynamics of COS in the global atmosphere, and measurements of ecosystem fluxes of COS.

Principal Investigator

J. Elliott Campbell
University of California, Santa Cruz

Program Manager

Daniel Stover
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science


Terrestrial Ecosystem Science program of the Office of Biological and Environmental Research, within the U.S. Department of Energy Office of Science, under Contract No. DE-SC0011999.


Campbell, J. E., J. Kesselmeier, D. Yakir, and J. O. Berry, et al. "Assessing a new clue to how much carbon plants take up". Eos 98 (10), 24–29  (2017). https://doi.org/10.1029/2017EO075313.