Abstract
AbstractTwo questions motivated this study: 1) Will meteorological droughts become more frequent and severe during the twenty-first century? 2) Given the projected global temperature rise, to what extent does the inclusion of temperature (in addition to precipitation) in drought indicators play a role in future meteorological droughts? To answer, we analyzed the changes in drought frequency, severity, and historically undocumented extreme droughts over 1981–2100, using the standardized precipitation index (SPI; including precipitation only) and standardized precipitation-evapotranspiration index (SPEI; indirectly including temperature), and under two representative concentration pathways (RCP4.5 and RCP8.5). As input data, we employed 103 high-resolution (0.44°) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), based on a combination of 16 global circulation models (GCMs) and 20 regional circulation models (RCMs). This is the first study on global drought projections including RCMs based on such a large ensemble of RCMs. Based on precipitation only, ~15% of the global land is likely to experience more frequent and severe droughts during 2071–2100 versus 1981–2010 for both scenarios. This increase is larger (~47% under RCP4.5, ~49% under RCP8.5) when precipitation and temperature are used. Both SPI and SPEI project more frequent and severe droughts, especially under RCP8.5, over southern South America, the Mediterranean region, southern Africa, southeastern China, Japan, and southern Australia. A decrease in drought is projected for high latitudes in Northern Hemisphere and Southeast Asia. If temperature is included, drought characteristics are projected to increase over North America, Amazonia, central Europe and Asia, the Horn of Africa, India, and central Australia; if only precipitation is considered, they are found to decrease over those areas.
Highlights
The latter decades of the twentieth century and the early years of the twenty-first century have seen many extreme weather events, among which heat waves and extreme precipitation in particular have become increasingly frequent in many global areas (IPCC 2014)
This study aims to answer the following question: where and to what extent will the projected temperature rise (IPCC 2014) play a crucial role in increased drought frequency and severity? Similar to a previous study focused on Europe (Spinoni et al 2018), here we separately investigated drought projections based on both standardized precipitation index (SPI; McKee et al 1993) and standardized precipitation-evapotranspiration index (SPEI; Vicente-Serrano et al 2010), in order to evaluate the importance of including temperature in drought projections
CRUTS includes potential evapotranspiration (PET), computed based on the Penman–Monteith method, we used minimum and maximum temperature data to obtain PET based on the Hargreaves–Samani equation, and in turn, SPI and SPEI, to ensure homogeneity with the CORDEX outputs
Summary
The latter decades of the twentieth century and the early years of the twenty-first century have seen many extreme weather events, among which heat waves and extreme precipitation in particular have become increasingly frequent in many global areas (IPCC 2014). Compared to other natural disasters such as floods or storms, detecting and quantifying droughts is more complex, since droughts are characterized by a slow onset and a high resilience to their effects, while long-term impacts may emerge months or even years after the drought peak (Vogt and Somma 2000; Wilhite 2000; Wilhite et al 2007). Another level of complexity arises from the many different definitions of drought, including meteorological, agricultural, hydrological, socioeconomic, and ecological droughts (Mishra and Singh 2010; Crausbay et al 2017). The recognition of drought as a climate hazard, as well as a better understanding of its manifold aspects, is becoming an urgent priority in a warming world (Dai 2011), with the result that drought is becoming a ‘‘hot topic’’ in climatology (Trenberth et al 2014)
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