Abstract
Abstract. The 2015 Paris Agreement proposed a more ambitious climate change mitigation target on limiting global warming to 1.5 ∘C instead of 2 ∘C above preindustrial levels. Scientific investigations on environmental risks associated with these warming targets are necessary to inform climate policymaking. Based on the Coupled Model Intercomparison Project phase 5 (CMIP5) climate models, we present the first risk-based assessment of changes in global drought and the impact of severe drought on populations from additional 1.5 and 2 ∘C warming conditions. Our results highlight the risk of drought on a global scale and in several hotspot regions such as the Amazon, northeastern Brazil, southern Africa and Central Europe at both 1.5 and 2 ∘C global warming relative to the historical period, showing increases in drought durations from 2.9 to 3.2 months. Correspondingly, more total and urban populations would be exposed to severe droughts globally (+132.5 ± 216.2 million and +194.5 ± 276.5 million total population and +350.2 ± 158.8 million and +410.7 ± 213.5 million urban populations in 1.5 and 2 ∘C warmer worlds) and regionally (e.g., East Africa, West Africa and South Asia). Less rural populations (−217.7 ± 79.2 million and −216.2 ± 82.4 million rural populations in 1.5 and 2 ∘C warmer worlds) would be exposed to severe drought globally under climate warming, population growth and especially the urbanization-induced population migration. By keeping global warming at 1.5 ∘C above the preindustrial levels instead of 2 ∘C, there is a decrease in drought risks (i.e., less drought duration, less drought intensity and severity but relatively more frequent drought) and the affected total, urban and rural populations would decrease globally and in most regions. While challenging for both East Africa and South Asia, the benefits of limiting warming to below 1.5 ∘C in terms of global drought risk and impact reduction are significant.
Highlights
Drought could bring adverse consequences to water supply, food production and the environment as a whole (Wang et al, 2011; Sheffield et al, 2012)
The geographic pattern of changes in the Palmer Drought Severity Index (PDSI) for the 2 ◦C warmer world is quite similar to that of 1.5 ◦C warmer world, but the magnitude of change would intensify in both directions in East Canada, Greenland, Iceland (−0.3 ± 0.2 → −0.4 ± 0.2), East Africa (−0.5 ± 0.2 → −0.3 ± 0.2), Northern Europe (−0.3 ± 0.3 → −0.2 ± 0.3), East Asia (−0.3 ± 0.1 → −0.2 ± 0.4), South Asia (−1.0 ± 1.2 → −0.8 ± 0.3) and West Africa (−0.3 ± 0.2 → −0.3 ± 0.3)
When global warming is capped at 1.5 ◦C instead of 2 ◦C above the preindustrial levels, the PDSI value would elevate globally
Summary
Drought could bring adverse consequences to water supply, food production and the environment as a whole (Wang et al, 2011; Sheffield et al, 2012) Because of these serious consequences, severe droughts in the recent past have gained wide attention. Regardless of the socioeconomic and political achievability of these goals (Sanderson et al, 2017), there is a lack of scientific knowledge about the relative risks (e.g., drought risks and their potential impacts) associated with the implications of 1.5 and 2 ◦C warming This has naturally attracted contributions from the scientific community (Hulme, 2016; Schleussner et al, 2016; Peters, 2016; King et al, 2017)
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