There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.
Radiative effects of anthropogenic changes in atmospheric composition are expected
to cause climate changes, in particular an intensification of the global water cycle
with a consequent increase in flood risk. But the detection of anthropogenically forced
changes in flooding is difficult because of the substantial natural variability; the
dependence of streamflow trends on flow regime 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 km(2)--using both streamflow
measurements and numerical simulations of the anthropogenic climate change associated
with greenhouse gases and direct radiative effects of sulphate aerosols. 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.