A new framework for drought definition, identification, and preparedness

Climate change has led to new forms of extreme that until recently were not a topic of concern for the scientific community and general society. Terms such as flash droughts, megadrought, and anthropogenic droughts, among others, entered our vocabulary only recently, in the past decade or so. However, such categorizations are unclear and only come after the fact and with a considerable delay between impacts and definition, hindering preparedness potential. By the current projections and actions regarding climate change, one can only assume that extreme events of different magnitudes, multiple drivers and extensive impacts will keep surprising us. We propose in this work a novel frame to define extreme events. The aim is to allow their identification and increase preparedness against their impacts. The premise is to invert the pyramid of priorities and (1) in collaboration with stakeholders, policymakers and society, assess the potential impacts, defining different levels of “damage”. (2) From the identified levels of impact, use historical data, modelling, and projections to assess frequencies and drivers. Finally, (3) define the thresholds and patterns that lead to such impacts, supporting informed mitigation action and forecast. We present two examples of the application of this methodology regarding crop production in Germany. First, we identify what dry spell duration, thresholds, and seasonality are critical to crop yield. In the second, we identify the flashiness and intensity of flash droughts that lead to increasing crop losses, besides environmental drives to such events. This approach provides better results in identifying and defining such events. It also equips scientists with more didactic and direct measures of extreme events, facilitating communication and empowering action.