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Australian climate–carbon cycle feedback reduced by soil black carbon

Nature Geoscience volume 1, pages 832835 (2008) | Download Citation



Annual emissions of carbon dioxide from soil organic carbon are an order of magnitude greater than all anthropogenic carbon dioxide emissions taken together1. Global warming is likely to increase the decomposition of soil organic carbon, and thus the release of carbon dioxide from soils2,3,4,5, creating a positive feedback6,7,8,9. Current models of global climate change that recognize this soil carbon feedback are inaccurate if a larger fraction of soil organic carbon than postulated has a very slow decomposition rate. Here we show that by including realistic stocks of black carbon in prediction models, carbon dioxide emissions are reduced by 18.3 and 24.4% in two Australian savannah regions in response to a warming of 3 C over 100 years1. This reduction in temperature sensitivity, and thus the magnitude of the positive feedback, results from the long mean residence time of black carbon, which we estimate to be approximately 1,300 and 2,600 years, respectively. The inclusion of black carbon in climate models is likely to require spatially explicit information about its distribution, given that the black carbon content of soils ranged from 0 to 82% of soil organic carbon in a continental-scale analysis of Australia. We conclude that accurate information about the distribution of black carbon in soils is important for projections of future climate change.

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This research was financially supported by CSIRO, Bureau of Rural Sciences, Grains Research and Development Corporation, and the Australian Greenhouse Office. J.L. was supported by a Sir Frederick McMaster Fellowship from CSIRO, and acknowledges partial support by a USDA-NACP grant. Rothamsted Research receives grant-aided support from the Biotechnology and Biological Sciences Research Council (BBSRC). P.F. was supported by the Joint DECC and MoD Program. Suggestions from D. Jenkinson and K. Broos are much appreciated.

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  1. Department of Crop and Soil Sciences, College of Agriculture and Life Sciences, Cornell University, Ithaca, New York 14853, USA

    • Johannes Lehmann
    •  & Peter Woodbury
  2. CSIRO Land and Water, Glen Osmond, SA 5064, Australia

    • Jan Skjemstad
    •  & Evelyn Krull
  3. Rothamsted Research, Harpenden, AL5 2JQ, UK

    • Saran Sohi
    •  & Kevin Coleman
  4. Queensland Climate Change Centre of Excellence, Environmental Protection Agency, Indooroopilly, Qld 4068, Australia

    • John Carter
  5. Bureau of Rural Sciences, Department of Agriculture, Fisheries and Forestry, Canberra, ACT 2602, Australia

    • Michele Barson
  6. Met Office Hadley Centre, Fitzroy Road, Exeter EX1 3PB, UK

    • Pete Falloon


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J.L., S.S., P.F., P.W. and K.C. planned the temperature response modelling. J.S. and M.B. planned and conducted the soil assessments, J.S. and E.K. conducted the soil analyses. J.C. contributed the vegetation model. J.L. and J.S. provided the modelling framework and analysed the data. J.L. developed the manuscript and J.S., S.S., P.F., K.C., P.W., K.C. and E.K. provided input to the manuscript.

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Correspondence to Johannes Lehmann.

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