Letter | Published:

Agricultural Green Revolution as a driver of increasing atmospheric CO2 seasonal amplitude

Nature volume 515, pages 394397 (20 November 2014) | Download Citation



The atmospheric carbon dioxide (CO2) record displays a prominent seasonal cycle that arises mainly from changes in vegetation growth and the corresponding CO2 uptake during the boreal spring and summer growing seasons and CO2 release during the autumn and winter seasons1,2,3,4. The CO2 seasonal amplitude has increased over the past five decades, suggesting an increase in Northern Hemisphere biospheric activity2,5,6. It has been proposed that vegetation growth may have been stimulated by higher concentrations of CO2 as well as by warming in recent decades, but such mechanisms have been unable to explain the full range and magnitude of the observed increase in CO2 seasonal amplitude2,6,7,8,9,10,11,12,13. Here we suggest that the intensification of agriculture (the Green Revolution, in which much greater crop yield per unit area was achieved by hybridization, irrigation and fertilization) during the past five decades is a driver of changes in the seasonal characteristics of the global carbon cycle. Our analysis of CO2 data and atmospheric inversions shows a robust 15 per cent long-term increase in CO2 seasonal amplitude from 1961 to 2010, punctuated by large decadal and interannual variations. Using a terrestrial carbon cycle model that takes into account high-yield cultivars, fertilizer use and irrigation, we find that the long-term increase in CO2 seasonal amplitude arises from two major regions: the mid-latitude cropland between 25° N and 60° N and the high-latitude natural vegetation between 50° N and 70° N. The long-term trend of seasonal amplitude increase is 0.311 ± 0.027 per cent per year, of which sensitivity experiments attribute 45, 29 and 26 per cent to land-use change, climate variability and change, and increased productivity due to CO2 fertilization, respectively. Vegetation growth was earlier by one to two weeks, as measured by the mid-point of vegetation carbon uptake, and took up 0.5 petagrams more carbon in July, the height of the growing season, during 2001–2010 than in 1961–1970, suggesting that human land use and management contribute to seasonal changes in the CO2 exchange between the biosphere and the atmosphere.

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We thank all data providers, especially the NOAA CO2 and CarbonTracker team, and the Jena inversion team. M. Heimann suggested the flux data site comparison. This research was supported by NOAA (NA10OAR4310248 and NA09NES4400006), the NSF (AGS-1129088), and NASA (NNH12AU35I).

Author information


  1. Department of Atmospheric and Oceanic Science, and Earth System Science Interdisciplinary Center, University of Maryland, College Park, Maryland 20742, USA

    • Ning Zeng
    • , Fang Zhao
    • , Eugenia Kalnay
    •  & Ross J. Salawitch
  2. Hydrospheric and Biospheric Sciences, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA

    • George J. Collatz
  3. Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, Maryland 20740, USA

    • Tristram O. West
  4. Institute for Space Sciences, Freie Universität Berlin, 12165 Berlin, Germany

    • Luis Guanter


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N.Z. designed the research and all authors contributed to the ideas. N.Z. and F.Z. conducted the simulations and data analysis. L.G. analysed the TRENDY models and satellite SIF data. N.Z. wrote the paper with input from all others.

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The authors declare no competing financial interests.

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Correspondence to Ning Zeng.

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