Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Projected increase in continental runoff due to plant responses to increasing carbon dioxide


In addition to influencing climatic conditions directly through radiative forcing, increasing carbon dioxide concentration influences the climate system through its effects on plant physiology1. Plant stomata generally open less widely under increased carbon dioxide concentration2, which reduces transpiration1,3,4,5,6 and thus leaves more water at the land surface7. This driver of change in the climate system, which we term ‘physiological forcing’, has been detected in observational records of increasing average continental runoff over the twentieth century8. Here we use an ensemble of experiments with a global climate model that includes a vegetation component to assess the contribution of physiological forcing to future changes in continental runoff, in the context of uncertainties in future precipitation. We find that the physiological effect of doubled carbon dioxide concentrations on plant transpiration increases simulated global mean runoff by 6 per cent relative to pre-industrial levels; an increase that is comparable to that simulated in response to radiatively forced climate change (11 ± 6 per cent). Assessments of the effect of increasing carbon dioxide concentrations on the hydrological cycle that only consider radiative forcing9,10,11 will therefore tend to underestimate future increases in runoff and overestimate decreases. This suggests that freshwater resources may be less limited than previously assumed under scenarios of future global warming, although there is still an increased risk of drought. Moreover, our results highlight that the practice of assessing the climate-forcing potential of all greenhouse gases in terms of their radiative forcing potential relative to carbon dioxide does not accurately reflect the relative effects of different greenhouse gases on freshwater resources.

Access options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Impact of physiological forcing on global mean runoff, precipitation and temperature.
Figure 2: Impact of physiological forcing on relationship between changes in runoff and precipitation on doubling CO2.


  1. 1

    Sellers, P. J. et al. Comparison of radiative and physiological effects of doubled atmospheric CO2 on climate. Science 271, 1402–1406 (1996)

    ADS  CAS  Article  Google Scholar 

  2. 2

    Field, C., Jackson, R. & Mooney, H. Stomatal responses to increased CO2: implications from the plant to the global scale. Plant Cell Environ. 18, 1214–1255 (1995)

    Article  Google Scholar 

  3. 3

    Betts, R. A., Cox, P. M., Lee, S. E. & Woodward, F. I. Contrasting physiological and structural vegetation feedbacks in climate change simulations. Nature 387, 796–799 (1997)

    ADS  CAS  Article  Google Scholar 

  4. 4

    Cox, P. M. et al. The impact of new land surface physics on the GCM simulation of climate and climate sensitivity. Clim. Dyn. 15, 183–203 (1999)

    Article  Google Scholar 

  5. 5

    Hungate, B. A. et al. Evapotranspiration and soil water content in a scrub-oak woodland under carbon dioxide enrichment. Glob. Change Biol. 8, 289–298 (2002)

    ADS  Article  Google Scholar 

  6. 6

    Long, S. P., Ainsworth, E. A., Leakey, A. D. B., Nösberger, J. & Ort, D. R. Food for thought: lower-than-expected crop yield stimulation with rising CO2 concentrations. Science 312, 1918–1921 (2006)

    ADS  CAS  Article  Google Scholar 

  7. 7

    Wigley, T. M. L. & Jones, P. D. Influences of precipitation changes and direct CO2 effects on streamflow. Nature 314, 149–152 (1985)

    ADS  CAS  Article  Google Scholar 

  8. 8

    Gedney, N. et al. Detection of a direct carbon dioxide effect in continental river runoff records. Nature 439, 835–838 (2006)

    ADS  CAS  Article  Google Scholar 

  9. 9

    Arnell, N. et al. Hydrology and water resources. In Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change Ch.4 191–234 (Cambridge Univ. Press, Cambridge, UK, 2001)

    Google Scholar 

  10. 10

    Warren, R. Impacts of global climate change at different annual mean global temperature increases. In Avoiding Dangerous Climate Change (eds Schellnhuber, H. J., Cramer, W., Nakicenovic, N., Wigley, T. & Yohe, G.) Ch.11 93–100 (Cambridge Univ. Press, Cambridge, UK, 2006)

    Google Scholar 

  11. 11

    De Wit, M. & Stankiewicz, J. Changes in surface water supply across Africa with predicted climate change. Science 311, 1917–1921 (2006)

    ADS  CAS  Article  Google Scholar 

  12. 12

    Murphy, J. M. et al. Quantification of modelling uncertainties in a large ensemble of climate change simulations. Nature 430, 768–772 (2004)

    ADS  CAS  Article  Google Scholar 

  13. 13

    Webb, M. J. et al. On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles. Clim. Dyn. 27 (1). 17–38 (2006)

    Article  Google Scholar 

  14. 14

    Collatz, G. J., Ball, J. T., Grivet, C. & Berry, J. A. Physiological and environmental regulation of stomatal conductance, photosynthesis and transpiration: A model that includes a laminar boundary layer. Agric. Forest. Meteorol. 54, 107–136 (1991)

    ADS  Article  Google Scholar 

  15. 15

    Collatz, G. J., Ribas-Carbo, M. & Berry, J. A. A coupled photosynthesis-stomatal conductance model for leaves of C4 plants. Aust. J. Plant Physiol. 19, 519–538 (1992)

    Google Scholar 

  16. 16

    Jacobs, C. Direct Impacts of Atmospheric CO2 Enrichment on Regional Transpiration. PhD thesis, Wageningen Agricultural Univ. (1994)

  17. 17

    Sellers, P. J., Berry, J., Collatz, G., Field, C. & Hall, F. Canopy reflectance, photosynthesis and transpiration. III. A reanalysis using enzyme kinetics–electron transport models of leaf physiology. Remote Sensing Environ. 42, 187–216 (1992)

    ADS  Article  Google Scholar 

  18. 18

    Cramer, W. et al. Global response of terrestrial ecosystem structure and function to CO2 and climate change: results from six dynamic global vegetation models. Glob. Change Biol. 7, 357–374 (2001)

    ADS  Article  Google Scholar 

  19. 19

    Betts, R. A. et al. The role of ecosystem-atmosphere interactions in simulated Amazonian precipitation decrease and forest dieback under global climate warming. Theor. Appl. Climatol. 78, 157–175 (2004)

    ADS  Article  Google Scholar 

  20. 20

    Betts, R. A. Self-beneficial effects of vegetation on climate in an ocean-atmosphere General Circulation Model. Geophys. Res. Lett. 26, 1457–1460 (1999)

    ADS  Article  Google Scholar 

  21. 21

    Leipprand, A. & Gerten, D. Global effects of doubled atmospheric CO2 content on evapotranspiration, soil moisture and runoff under potential natural vegetation. Hydrol. Sci. 51, 171–185 (2006)

    CAS  Article  Google Scholar 

  22. 22

    Betts, R. A., Cox, P. M. & Woodward, F. I. Simulated responses of potential vegetation to doubled-CO2 climate change and feedbacks on near-surface temperature. Glob. Ecol. Biogeogr. 9, 171–180 (2000)

    Article  Google Scholar 

  23. 23

    Douville, H. et al. Importance of vegetation feedbacks in doubled-CO2 climate experiments. J. Geophys. Res. 105 (D11). 14841–14861 (2000)

    ADS  CAS  Article  Google Scholar 

  24. 24

    Cox, P. M . Description of the Triffid Dynamic Global Vegetation Model. Technical Note 24 (Met Office Hadley Centre, Bracknell, 2001); 〈

  25. 25

    Cox, P. M., Betts, R. A., Jones, C. D., Spall, S. A. & Totterdell, I. J. Acceleration of global warming due to carbon-cycle feedbacks in a coupled climate model. Nature 408, 184–187 (2000)

    ADS  CAS  Article  Google Scholar 

  26. 26

    IPCC. Climate Change 1994: Radiative Forcing of Climate Change and an Evaluation of the IPCC IS92 Emission Scenarios (Cambridge Univ. Press, Cambridge, UK, 1994)

  27. 27

    United Nations Framework Convention on Climate Change. UNFCCC Article 2. Report no. UNEP/IUC/99/2 (Information Unit for Conventions, UNEP, Geneva, 1999); 〈〉.

  28. 28

    Forster, P. et al. in Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (eds Solomon, S. et al.) Ch. 2 (Cambridge Univ. Press, Cambridge, UK/New York, USA, 2007)

    Google Scholar 

  29. 29

    Roderick, M. J. & Farquhar, G. D. The cause of decreased pan evaporation over the past 50 years. Science 298, 1410–1411 (2002)

    ADS  CAS  PubMed  Google Scholar 

  30. 30

    IPCC. Climate Change 2007: Impacts, Adaptation and Vulnerability. Working Group II Contribution to the Intergovernmental Panel on Climate Change, Fourth Assessment Report (Cambridge Univ. Press, Cambridge, UK, 2007)

Download references


We thank G. Dupre, D. Matthews, A. Nobre, C. Rye, M. Sanderson, S. Sitch and T. Wheeler for comments. This work was supported by the UK Ministry of Defence project “Defence and Security Implications of Climate Change” and the Climate Prediction Programme of the UK Department for Environment, Food and Rural Affairs. P.M.C. and C.H. were supported by the UK Natural Environment Research Council.

Author Contributions R.A.B. proposed the study, performed the dynamic vegetation simulations and led the analysis and writing. D.L.H. performed statistical analysis of the ensemble simulations and contributed expertise on field experiments on plant physiology. P.D.F. analysed the dynamic vegetation simulations. P.M.C. developed the MOSES and TRIFFID models and contributed to the interpretation. C.D.J., N.G., C.H. and O.B. contributed to the analysis and provided further expertise on modelling plant physiology, hydrology and land–atmosphere interactions. M.C., D.M.H.S. and M.J.W. designed and performed the ensemble simulations and advised on their interpretation. All co-authors contributed to the text.

Author information



Corresponding author

Correspondence to Richard A. Betts.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Tables

This file contains Supplementary Tables 1-6 showing impacts of physiological forcing on global mean precipitation, runoff and runoff/precipitation ratio for each continent except Antarctica. (PDF 107 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Betts, R., Boucher, O., Collins, M. et al. Projected increase in continental runoff due to plant responses to increasing carbon dioxide. Nature 448, 1037–1041 (2007).

Download citation

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing