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A framework for assessing uncertainties in climate change impacts: low flow scenarios for the River Thames.

Research output: Contribution to journalJournal articlepeer-review

Published
  • Robert Wilby
  • I. Harris
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<mark>Journal publication date</mark>1/02/2006
<mark>Journal</mark>Water Resources Research
Issue number2
Volume42
Pages (from-to)W02419
Publication StatusPublished
<mark>Original language</mark>English

Abstract

A probabilistic framework is presented for combining information from an ensemble of four general circulation models (GCMs), two greenhouse gas emission scenarios, two statistical downscaling techniques, two hydrological model structures, and two sets of hydrological model parameters. GCMs were weighted according to an index of reliability for downscaled effective rainfall, a key determinant of low flows in the River Thames. Hydrological model structures were weighted by performance at reproducing annual low-flow series. Weights were also assigned to sets of water resource model (CATCHMOD) parameters using the Nash-Sutcliffe efficiency criterion. Emission scenarios and downscaling methods were unweighted. A Monte Carlo approach was then used to explore components of uncertainty affecting projections for the River Thames by the 2080s. The resulting cumulative distribution functions (CDFs) of low flows were most sensitive to uncertainty in the climate change scenarios and downscaling of different GCMs. Uncertainties due to the hydrological model parameters and emission scenario increase with time but were less important. Abrupt changes in low-flow CDFs were attributed to uncertainties in statistically downscaled summer rainfall. This was linked to different behavior of atmospheric moisture among the chosen GCMs.

Bibliographic note

This paper sets out a probabilistic framework for characterising from climate model, emission scenario, downscaling method, hydrological model structure and paremeterisation uncertainties in water resource assessments. The work is an early step towards applying next generation probabilistic climate change information. Harris processed the raw climate model outputs. RAE_import_type : Journal article RAE_uoa_type : Earth Systems and Environmental Sciences