Large historical growth in global terrestrial gross primary production.
Campbell, J. E. 1, c1; Berry, J. A. 2; Seibt, U. 3; Smith, S. J. 4; Montzka, S. A. 5; Launois, T. 6, *; Belviso, S. 6; Bopp, L. 6, *; Laine, M. 7
[Letter] Nature. 544(7648):84-87, April 6, 2017.

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: Growth in terrestrial gross primary production (GPP)-the amount of carbon dioxide that is 'fixed' into organic material through the photosynthesis of land plants-may provide a negative feedback for climate change 1,2. It remains uncertain, however, to what extent biogeochemical processes can suppress global GPP growth 3. As a consequence, modelling estimates of terrestrial carbon storage, and of feedbacks between the carbon cycle and climate, remain poorly constrained 4. Here we present a global, measurement-based estimate of GPP growth during the twentieth century that is based on long-term atmospheric carbonyl sulfide (COS) records, derived from ice-core, firn and ambient air samples 5. We interpret these records using a model that simulates changes in COS concentration according to changes in its sources and sinks-including a large sink that is related to GPP. We find that the observation-based COS record is most consistent with simulations of climate and the carbon cycle that assume large GPP growth during the twentieth century (31% /- 5% growth; mean /- 95% confidence interval). Although this COS analysis does not directly constrain models of future GPP growth, it does provide a global-scale benchmark for historical carbon-cycle simulations.

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