Can we calculate drought risk ... and do we need to?

There is growing interest in the possibility of global analysis of drought risk, following the rapid development of global models of flood risk and other natural hazards. While this is an attractive idea, we argue that it is not actually possible as, unlike for flooding, it is not possible to unambiguously distinguish between drought and nondrought events, in particular when considering the impacts of droughts on agriculture. Any definition of a drought event depends upon the choice of drought index, which is to some extent arbitrary. Nonetheless, the absence of unambiguous quantified estimates of drought risk need not be an obstacle to rational drought risk management, as it is still possible to evaluate and compare the benefits of different drought risk management options. This article is categorized under: Science of Water > Water Extremes Science of Water > Water and Environmental Change Science of Water > Methods