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Hydrologic implications of vegetation response to elevated CO2 in climate projections

Nature Climate Changevolume 9pages4448 (2019) | Download Citation


Climate model projections using offline aridity and/or drought indices predict substantial terrestrial drying over the twenty-first century1,2,3,4,5,6,7,8,9,10,11. However, these same models also predict an increased runoff12,13,14,15. This contradiction has been linked to an absence of vegetation responses to an elevated atmospheric CO2 concentration [CO2] in offline impact models12,14,16,17. Here we report a close and consistent relationship between changes in surface resistance (rs) and [CO2] across 16 CMIP5 models. Attributing evapotranspiration changes under non-water-limited conditions shows that an increase in evapotranspiration caused by a warming-induced vapour pressure deficit increase18 is almost entirely offset by a decrease in evapotranspiration caused by increased rs driven by rising [CO2]. This indicates that climate models do not actually project increased vegetation water use under an elevated [CO2], which counters the perception that ‘warming leads to drying’ in many previous studies1,2,3,4,5,6,7,8,9,10,11. Moreover, we show that the hydrologic information in CMIP5 models can be satisfactorily recovered using an offline hydrologic model that incorporates the [CO2] effect on rs in calculating potential evapotranspiration (EP). This offers an effective, physically-based yet relatively simple way to account for the vegetation response to elevated [CO2] in offline impact models.

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The CMIP5 model outputs are available from the CMIP5 archive (http://cmip-pcmdi.llnl.gov/cmip5/).

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Y.Y. and M.R. acknowledge the support of the Australian Research Council (CE1101028, CE170100023). T.M. and R.D. acknowledge the support from CSIRO Land and Water.

Author information

Author notes

    • Yuting Yang

    Present address: State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China


  1. Research School of Earth Sciences, Australian National University, Canberra, ACT, Australia

    • Yuting Yang
    •  & Michael L. Roderick
  2. Australian Research Council Centre of Excellence for Climate System Science, Canberra, ACT, Australia

    • Yuting Yang
    • , Michael L. Roderick
    • , Tim R. McVicar
    •  & Randall J. Donohue
  3. Australian Research Council Centre of Excellence for Climate Extremes, Canberra, ACT, Australia

    • Michael L. Roderick
  4. State Key Laboratory of Hydroscience and Engineering, Department of Hydraulic Engineering, Tsinghua University, Beijing, China

    • Shulei Zhang
  5. CSIRO Land and Water, Black Mountain, Canberra, ACT, Australia

    • Tim R. McVicar
    •  & Randall J. Donohue


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Y.Y., M.R., T.M. and R.D. conceived the idea. Y.Y. and M.R. designed the study. Y.Y. and S.Z. performed the analyses. Y.Y. drafted the manuscript. All the authors contributed to results, discussion and manuscript writing.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Yuting Yang or Michael L. Roderick.

Supplementary information

  1. Supplementary Information

    Supplementary Tables 1–2, Supplementary Figures 1–8, Supplementary Note 1, Supplementary References

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