Abstract
Abstract. This paper assesses the relationship between amount of climate forcing – as indexed by global mean temperature change – and hydrological response in a sample of UK catchments. It constructs climate scenarios representing different changes in global mean temperature from an ensemble of 21 climate models assessed in the IPCC AR4. The results show a considerable range in impact between the 21 climate models, with – for example – change in summer runoff at a 2 °C increase in global mean temperature varying between −40% and +20%. There is evidence of clustering in the results, particularly in projected changes in summer runoff and indicators of low flows, implying that the ensemble mean is not an appropriate generalised indicator of impact, and that the standard deviation of responses does not adequately characterise uncertainty. The uncertainty in hydrological impact is therefore best characterised by considering the shape of the distribution of responses across multiple climate scenarios. For some climate model patterns, and some catchments, there is also evidence that linear climate change forcings produce non-linear hydrological impacts. For most variables and catchments, the effects of climate change are apparent above the effects of natural multi-decadal variability with an increase in global mean temperature above 1 °C, but there are differences between catchments. Based on the scenarios represented in the ensemble, the effect of climate change in northern upland catchments will be seen soonest in indicators of high flows, but in southern catchments effects will be apparent soonest in measures of summer and low flows. The uncertainty in response between different climate model patterns is considerably greater than the range due to uncertainty in hydrological model parameterisation.
Highlights
The literature contains hundreds of examples of the potential impact of future climate change on hydrological regimes, in an increasingly wide variety of environments (Kundzewicz et al, 2007; Bates et al, 2008)
The aim of this paper is to examine the relationship between climate forcing – as indexed by change in global average temperature – and hydrological response, using six case study catchments representing different hydrological characteristics in the UK, and multiple climate scenarios derived from the climate models evaluated in the IPCC’s Fourth Assessment Report (IPCC, 2007)
This paper has examined the effect of climate change on river flow characteristics in a sample of UK catchments, using a large number of climate scenarios scaled to represent progressively increasing amounts of climate change
Summary
The literature contains hundreds of examples of the potential impact of future climate change on hydrological regimes, in an increasingly wide variety of environments (Kundzewicz et al, 2007; Bates et al, 2008). The aim of this paper is to examine the relationship between climate forcing – as indexed by change in global average temperature – and hydrological response, using six case study catchments representing different hydrological characteristics in the UK, and multiple climate scenarios derived from the climate models evaluated in the IPCC’s Fourth Assessment Report (IPCC, 2007). These scenarios are scaled to represent prescribed changes in global average temperature ranging from 0.5 ◦C (above 1961–1990) to 6 ◦C. The paper complements papers by Kingston and Taylor (2010), Kingston et al (2010), Hughes et al (2010), Nobrega et al (2011), Singh et al (2010), Thorne (2010) and Xu et al (2011) which all follow the same methodology (Todd et al, 2010) in different catchments
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