From climate model ensembles to climate change impacts and adaptation: A case study of water resource management in the southwest of England

Abstract

[1] The majority of climate change impacts and adaptation studies so far have been based on at most a few deterministic realizations of future climate, usually representing different emissions scenarios. Large ensembles of climate models are increasingly available either as ensembles of opportunity or perturbed physics ensembles, providing a wealth of additional data that is potentially useful for improving adaptation strategies to climate change. Because of the novelty of this ensemble information, there is little previous experience of practical applications or of the added value of this information for impacts and adaptation decision making. This paper evaluates the value of perturbed physics ensembles of climate models for understanding and planning public water supply under climate change. We deliberately select water resource models that are already used by water supply companies and regulators on the assumption that uptake of information from large ensembles of climate models will be more likely if it does not involve significant investment in new modeling tools and methods. We illustrate the methods with a case study on the Wimbleball water resource zone in the southwest of England. This zone is sufficiently simple to demonstrate the utility of the approach but with enough complexity to allow a variety of different decisions to be made. Our research shows that the additional information contained in the climate model ensemble provides a better understanding of the possible ranges of future conditions, compared to the use of singlemodel scenarios. Furthermore, with careful presentation, decision makers will find the results from large ensembles of models more accessible and be able to more easily compare the merits of different management options and the timing of different adaptation. The overhead in additional time and expertise for carrying out the impacts analysis will be justified by the increased quality of the decision-making process. We remark that even though we have focused our study on a water resource system in the United Kingdom, our conclusions about the added value of climate model ensembles in guiding adaptation decisions can be generalized to other sectors and geographical regions.

Using UKCP09 probabilistic climate information for UK water resource planning

“…It has also been widely used in climate change impact assessments (Diaz-Nieto and Wilby, 2005;Wilby and Harris, 2006;New et al, 2007;Lopez et al, 2009;Manning et al, 2009). Catchmod works with different zones contributing to the output flow and corresponding to different paths, and this study makes use of models with 3 zones for fast, medium and slow paths with 5 parameters each.…”

Climate Change Risk Management in Transnational River Basins: The Rhine

“…In addition, also criteria like e.g. flexibility, costs and social acceptance are relevant for the selection and design of adaptation actions (Aerts and Droogers 2009;Lopez et al 2009). Formulating robust strategies will only be possible if knowledge is effectively shared between the scientific climate community and policymakers at the many relevant governance levels, from local to international.…”

“…When, for example, the result of the modelling on the right hand side of the figure indicates that it is likely that river discharges will increase, water managers can increase the height of dikes, which is in this case an adaptation strategy Another example is if water levels are projected to decrease, and measures are required to adapt inland shipping practices. However, adaptation choices will not only depend on the modelling result, but also on other factors, like costs, impacts on environment, public response and acceptance, technical feasibility and demographic and water use changes (Lopez et al 2009). These factors will be part of the negotiations in the governance process.…”

A framework for the quantitative assessment of climate change impacts on water-related activities at the basin scale

“…This is an annual correction function for the precipitation time series, and a seasonal correction function for the temperature time series. Figure 3 compares some statistics of the downscaled output of the RACMO RCM (Lenderink et al, 2003) over the backcast and forecast period. The forecast climate scenario shows an increase in monthly mean temperature (of about 4 • C) and a shift in the precipitation pattern (decrease in spring and summer and increase in autumn and winter) while the annual precipitation volume is only slightly lower than in the backcast scenario.…”

“…For instance, Arnell (2004) assesses the hydrological implications of climate change using several consistent climate and socio-economic scenarios. Brekke et al (2009) analyse projections from 17 different GCMs, while Lopez et al (2009) use an ensemble of projections of the same GCM under different parametrizations or perturbed physics ensembles. Dèquè et al (2007) compare the projection of many different RCMs on the European domain, while Bronstert et al (2007) compare three different downscaling methods to estimate the long-term water availability, drought conditions and floods.…”