High-end climate change impact on European runoff and low flows – exploring the effects of forcing biases

Lamprini V. Papadimitriou,Ioannis K. Tsanis,Manolis G. Grillakis,Aristeidis G. Koutroulis

doi:10.5194/hess-20-1785-2016

Lamprini V. Papadimitriou, Ioannis K. Tsanis + Show 2 more

Open Access

https://doi.org/10.5194/hess-20-1785-2016

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Abstract

Abstract. Climate models project a much more substantial warming than the 2 °C target under the more probable emission scenarios, making higher-end scenarios increasingly plausible. Freshwater availability under such conditions is a key issue of concern. In this study, an ensemble of Euro-CORDEX projections under RCP8.5 is used to assess the mean and low hydrological states under +4 °C of global warming for the European region. Five major European catchments were analysed in terms of future drought climatology and the impact of +2 °C versus +4 °C global warming was investigated. The effect of bias correction of the climate model outputs and the observations used for this adjustment was also quantified. Projections indicate an intensification of the water cycle at higher levels of warming. Even for areas where the average state may not considerably be affected, low flows are expected to reduce, leading to changes in the number of dry days and thus drought climatology. The identified increasing or decreasing runoff trends are substantially intensified when moving from the +2 to the +4° of global warming. Bias correction resulted in an improved representation of the historical hydrology. It is also found that the selection of the observational data set for the application of the bias correction has an impact on the projected signal that could be of the same order of magnitude to the selection of the Global Climate Model (GCM).

Highlights

Global CO2 emission rates have been following high-end climate change pathways leading to a future global temperature that is likely to surpass the target limit of 2 ◦C, despite the recent hiatus (England et al, 2015), and reach levels of +4 ◦C and higher at the end of the 21st century
Useful conclusions can be drawn from studies employing a single Global Hydrological Model (GHM)/land surface models (LSMs). Examples of such single model climate change impact assessments performed recently are the studies of Schneider et al (2013) and Laizé et al (2013) with the WaterGAP GHM, the studies of Arnell and Gosling (2013), Gosling and Arnell (2013) and Arnell et al (2013) with the GHM MacPDM and of Hanasaki et al (2010) using the H08 LSM
The future mean- and low-hydrological states under +4 ◦C of global warming were assessed for the European region, using the novel data set of the Euro-CORDEX climate projections

Summary

Introduction

Global CO2 emission rates have been following high-end climate change pathways leading to a future global temperature that is likely to surpass the target limit of 2 ◦C, despite the recent hiatus (England et al, 2015), and reach levels of +4 ◦C and higher at the end of the 21st century. It is projected that the number of people coping with significantly reduced water availability will increase by 15 % globally due to climate change, while the percentage of the global population living under conditions of absolute water scarcity is projected to increase (Schewe et al, 2014). In this framework, the future hydrological state needs to be assessed. Studies have shown that changes in runoff are not linearly correlated with changes in global mean temperature (Arnell and Gosling, 2013), nor are meteorological droughts with hydrological droughts (van Huijgevoort et al, 2013), concluding that for climate change impact assessments it is fundamental to use an impact model to translate the precipitation derived signal into runoff

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