Letter | Published:

Increasing risk of great floods in a changing climate

Nature volume 415, pages 514517 (31 January 2002) | Download Citation



Radiative effects of anthropogenic changes in atmospheric composition are expected to cause climate changes, in particular an intensification of the global water cycle1 with a consequent increase in flood risk2. But the detection of anthropogenically forced changes in flooding is difficult because of the substantial natural variability3; the dependence of streamflow trends on flow regime4,5 further complicates the issue. Here we investigate the changes in risk of great floods—that is, floods with discharges exceeding 100-year levels from basins larger than 200,000 km2—using both streamflow measurements and numerical simulations of the anthropogenic climate change associated with greenhouse gases and direct radiative effects of sulphate aerosols6. We find that the frequency of great floods increased substantially during the twentieth century. The recent emergence of a statistically significant positive trend in risk of great floods is consistent with results from the climate model, and the model suggests that the trend will continue.

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Streamflow data were collected and/or provided to us by the Global Runoff Data Centre (Germany), the US Geological Survey, Environment Canada, EarthInfo, Manaus Harbor Ltd/Portobras and Departmento Nacional de Aguas e Energia Electrica (Brazil), National Institute of Meteorology and Hydrology (Romania), J. Cordova, N. Garcia and J. Richey. We thank K. L. Findell, D. P. Lettenmaier and R. J. Stouffer for comments and suggestions.

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  1. *US Geological Survey, GFDL/NOAA, P.O. Box 308, Princeton, New Jersey 08542, USA

    • P. C. D. Milly
    •  & K. A. Dunne
  2. †Geophysical Fluid Dynamics Laboratory/NOAA, P.O. Box 308, Princeton, New Jersey 08542, USA

    • R. T. Wetherald
    •  & T. L. Delworth


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The authors declare no competing financial interests.

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Correspondence to P. C. D. Milly.

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