Global projections of drought hazard in a warming climate: a prime for disaster risk management

Projections of drought hazard (dH) changes have been mapped from five bias-corrected climate models and analyzed at the global level under three representative concentration pathways (RCPs). The motivation for this study is the observation that drought risk is increasing globally and the effective regulation of prevention and adaptation measures depends on dH magnitude and its distribution for the future. Based on the Weighted Anomaly of Standardized Precipitation index, dH changes have been assessed for mid-(2021-2050) and late-century (2071-2099). With a few exceptions, results show a likely increase in global dH between the historical years (1971-2000) and both future time periods under all RCPs. Notwithstanding this worsening trend, it was found that projections of dH changes for most regions are neither robust nor significant in the near-future. By the end of the century, greater increases are projected for RCPs describing stronger radiative forcing. Under RCP8.5, statistically significant dH changes emerge for global Mediterranean ecosystems and the Amazon region, which are identified as possible hotspots for future water security issues. Taken together, projections of dH changes point towards two dilemmas: (1) in the near-term, stake-holders are left worrying about projected increasing dH over large regions, but lack of actionable model agreement to take effective decisions related to local prevention and adaptation initiatives; (2) in the long-term, models demonstrate remarkable agreement, but stake-holders lack actionable knowledge to manage potential impacts far distant from actual human-dominated environments. We conclude that the major challenge for risk management is not to adapt human populations or their activities to dH changes, but to progress on global initiatives that mitigate their impacts in the whole carbon cycle by late-century.