Abstract
Abstract. Climate change very likely impacts future hydrological drought characteristics across the world. Here, we quantify the impact of climate change on future low flows and associated hydrological drought characteristics on a global scale using an alternative drought identification approach that considers adaptation to future changes in hydrological regime. The global hydrological model PCR-GLOBWB was used to simulate daily discharge at 0.5° globally for 1971–2099. The model was forced with CMIP5 climate projections taken from five global circulation models (GCMs) and four emission scenarios (representative concentration pathways, RCPs), from the Inter-Sectoral Impact Model Intercomparison Project. Drought events occur when discharge is below a threshold. The conventional variable threshold (VTM) was calculated by deriving the threshold from the period 1971–2000. The transient variable threshold (VTMt) is a non-stationary approach, where the threshold is based on the discharge values of the previous 30 years implying the threshold to vary every year during the 21st century. The VTMt adjusts to gradual changes in the hydrological regime as response to climate change. Results show a significant negative trend in the low flow regime over the 21st century for large parts of South America, southern Africa, Australia and the Mediterranean. In 40–52% of the world reduced low flows are projected, while increased low flows are found in the snow-dominated climates. In 27% of the global area both the drought duration and the deficit volume are expected to increase when applying the VTMt. However, this area will significantly increase to 62% when the VTM is applied. The mean global area in drought, with the VTMt, remains rather constant (11.7 to 13.4%), compared to the substantial increase when the VTM is applied (11.7 to 20%). The study illustrates that an alternative drought identification that considers adaptation to an altered hydrological regime has a substantial influence on future hydrological drought characteristics.
Highlights
Drought has large socio-economic and environmental impacts, e.g. on food, energy, water-born transport, ecosystem services, wildfires, and greenhouse gas emissions (e.g. Wilhite, 2000; Tallaksen and Van Lanen, 2004; Sheffield and Wood, 2011)
IPCC describes in the Special Report on EXtremes (IPCC-SREX) that droughts will intensify in the 21st century in certain seasons and areas as result of climate change (Seneviratne et al, 2012)
The objective of this study is to assess the impact of climate change on future hydrological drought across the globe under a changing hydrological regime, here represented using a transient threshold over the spatially distributed river discharge
Summary
Drought has large socio-economic and environmental impacts, e.g. on food (rainfed agriculture, irrigation), energy (hydropower, release of cooling water), water-born transport, ecosystem services, wildfires, and greenhouse gas emissions (e.g. Wilhite, 2000; Tallaksen and Van Lanen, 2004; Sheffield and Wood, 2011). Drought has large socio-economic and environmental impacts, e.g. on food (rainfed agriculture, irrigation), energy (hydropower, release of cooling water), water-born transport, ecosystem services, wildfires, and greenhouse gas emissions The 2011 drought in the Horn of Africa caused a large famine across the region leaving hundreds of thousands of people in need of assistance and with many regrettable fatalities (United Nations, 2011; Sida et al, 2012). Drought-related heat waves and forest fires caused almost 80 000 deaths in Europe in 2003. IPCC describes in the Special Report on EXtremes (IPCC-SREX) that droughts will intensify in the 21st century in certain seasons and areas (e.g. many European regions, parts of North America, Central America, southern Africa) as result of climate change (Seneviratne et al, 2012).
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