Detection of a direct carbon dioxide effect in continental river runoff records

Nature. 2006 Feb 16;439(7078):835-8. doi: 10.1038/nature04504.


Continental runoff has increased through the twentieth century despite more intensive human water consumption. Possible reasons for the increase include: climate change and variability, deforestation, solar dimming, and direct atmospheric carbon dioxide (CO2) effects on plant transpiration. All of these mechanisms have the potential to affect precipitation and/or evaporation and thereby modify runoff. Here we use a mechanistic land-surface model and optimal fingerprinting statistical techniques to attribute observational runoff changes into contributions due to these factors. The model successfully captures the climate-driven inter-annual runoff variability, but twentieth-century climate alone is insufficient to explain the runoff trends. Instead we find that the trends are consistent with a suppression of plant transpiration due to CO2-induced stomatal closure. This result will affect projections of freshwater availability, and also represents the detection of a direct CO2 effect on the functioning of the terrestrial biosphere.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon / metabolism
  • Carbon Dioxide / metabolism*
  • Ecosystem*
  • Geography
  • Greenhouse Effect*
  • Plant Transpiration
  • Plants / metabolism
  • Rain
  • Rivers*
  • Seawater / chemistry*
  • Time Factors
  • Water Supply


  • Carbon Dioxide
  • Carbon