A quantitative evaluation of the issue of drought definition: a source of disagreement in future drought assessments

  • Droughts are anticipated to intensify in many parts of the world due to climate change. However, the issue of drought definition, namely the diversity of drought indices, makes it difficult to compare drought assessments. This issue is widely known, but its relative importance has never been quantitatively evaluated in comparison to other sources of uncertainty. Here, encompassing three drought categories (meteorological, agricultural, and hydrological droughts) with four temporal scales of interest, we evaluated changes in the drought frequency using multi-model and multi-scenario simulations to identify areas where the definition issue could result in pronounced uncertainties and to what extent. We investigated the disagreement in the signs of changes between drought definitions and decomposed the variance into four main factors: drought definitions, greenhouse gas concentration scenarios, global climate models, and global water models, as well as their interactions. The results show that models were the primary sources of variance over 82% of the global land area. On the other hand, the drought definition was the dominant source of variance in the remaining 17%, especially in parts of northern high-latitudes. Our results highlight specific regions where differences in drought definitions result in a large spread among projections, including areas showing opposite signs of significant changes. At a global scale, 7% of the variance resulted independently from the definition issue, and that value increased to 44% when 1st and 2nd order interactions were considered. The quantitative results suggest that by clarifying hydrological processes or sectors of interest, one could avoid these uncertainties in drought assessments to obtain a clearer picture of future drought change.

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Author:Yusuke Satoh, Hideo Shiogama, Naota Hanasaki, Yadu Pokhrel, Julien Eric Stanislas Boulange, Peter Burek, Simon N. Gosling, Manolis Grillakis, Aristeidis Koutroulis, Hannes Müller SchmiedORCiDGND, Wim Thiery, Tokuta Yokohata
Parent Title (English):Environmental research letters
Publisher:IOP Publ.
Place of publication:Bristol
Document Type:Article
Date of Publication (online):2021/09/15
Date of first Publication:2021/09/15
Publishing Institution:Universitätsbibliothek Johann Christian Senckenberg
Release Date:2022/03/14
Tag:ANOVA; drought projections; sources of uncertainty; the issue of drought definition; uncertainty
Issue:art. 104001
Page Number:13
First Page:1
Last Page:13
This research is supported by the 'Integrated Research Program for Advancing Climate Models (TOUGOU Program)' sponsored by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), Japan (Grant No. JPMXD0717935715). This work was supported by Climate Change Adaptation research programs at National Institute for Environmental Studies. A. K. acknowledges the support from the FP7 project HELIX (Grant No. 603864). H.M.S acknowledges the support from the German Federal Ministry of Education and Research (BMBF, grant no. 01LS1711F). Y.P. acknowledges the support from the National Science Foundation (CAREER Award, Grant #. 1752729)
Institutes:Geowissenschaften / Geographie
Dewey Decimal Classification:5 Naturwissenschaften und Mathematik / 55 Geowissenschaften, Geologie / 550 Geowissenschaften
Licence (German):License LogoCreative Commons - Namensnennung 4.0