Guidelines for Studying Diverse Types of Compound Weather and Climate Events

Abstract

Compound weather and climate events are combinations of climate drivers and/or hazards that contribute to societal or environmental risk. Studying compound events often requires a multidisciplinary approach combining domain knowledge of the underlying processes with, for example, statistical methods and climate model outputs. Recently, to aid the development of research on compound events, four compound event types were introduced, namely (a) preconditioned, (b) multivariate, (c) temporally compounding, and (d) spatially compounding events. However, guidelines on how to study these types of events are still lacking. Here, we consider four case studies, each associated with a specific event type and a research question, to illustrate how the key elements of compound events (e.g., analytical tools and relevant physical effects) can be identified. These case studies show that (a) impacts on crops from hot and dry summers can be exacerbated by preconditioning effects of dry and bright springs. (b) Assessing compound coastal flooding in Perth (Australia) requires considering the dynamics of a non-stationary multivariate process. For instance, future mean sea-level rise will lead to the emergence of concurrent coastal and fluvial extremes, enhancing compound flooding risk. (c) In Portugal, deeplandslides are often caused by temporal clusters of moderate precipitation events. Finally, (d) crop yield failures in France and Germany are strongly correlated, threatening European food security through spatially compounding effects. These analyses allow for identifying general recommendations for studying compound events. Overall, our insights can serve as a blueprint for compound event analysis across disciplines and sectors.Plain Language Summary Many societal and environmental impacts from events such as droughts and storms arise from a combination of weather and climate factors referred to as a compound event. Considering the complex nature of these high-impact events is crucial for an accurate assessment of climate-related risk, for example to develop adaptation and emergency preparedness strategies. However, compound event research has emerged only recently, therefore our ability to analyze these events is still BEVACQUA ET AL.

The Precautionary Principles of the Potential Risks of Compound Events in Danish Municipalities

“…Fundamentally, each organisation manages its objectives through certain measures, such as instruments or tools. Bemelmans-Videc et al (1998) examine various (policy) instruments in different contexts and categorise them in a broad scheme. Policy instruments, also referred to as government tools, can be understood as the application of techniques to how public authorities exercise their power to achieve their goals and to initiate social change.…”

“…The analysis showed that each of the three municipalities created a different nuanced understanding of what a "compound event" means. In particular, the municipalities differ in their perception of what constitutes such a combined incident and what consequences it has for the local management and thus their risk management practices, which is also true for other European countries (Bevacqua et al, 2021). The three municipalities face different experiences, strategies, tools, and challenges in generally handling the risk of flooding and particularly compound flooding.…”

“…The conceptual idea of 'compound events' is not a particularly new phenomenon in disaster research and crisis management, as extreme events do rarely happen in isolation. In climate science, however, conventional research approaches were predominantly focused on single drivers or univariate hazards, to narrow research outputs and to reduce the complexity of climate dynamics, overseeing the potential risks stemming from dependent multiple climatic drivers (Zscheischler et al, 2018;Bevacqua et al, 2021).…”

Compound hot temperature and high chlorophyll extreme events in global lakes

“…One effort in this direction is the ongoing European Space Agency Climate Change Initiative for Lakes project, which coordinates a range of remote sensing techniques to develop time series data for multiple lake essential climate variables-including lake surface temperature, ice cover, water level/extent, and water-leaving reflectance. These data could allow further studies to explore diverse compound extreme events in lakes (Bevacqua et al 2021), and it provides good prospects for the impact of compound extremes to be better quantified and appreciated at a global scale. Overall, we hope that our contribution will stimulate wider efforts to understand the far-reaching global implications of compound extreme events, and their impacts on aquatic ecosystems.…”

Increasing spatiotemporal proximity of heat and precipitation extremes in a warming world quantified by a large model ensemble

“…These impacts can affect natural or societal systems, and act over spatial or temporal dimensions. Recent advances in theories of compounding (Raymond et al 2020, Thonicke et al 2020, Rusca et al 2021, Simpson et al 2021, in the statistics and dynamics of specific hazards (Bevacqua et al 2021), and in the analysis of co-occurrence of different hazard types (particularly drought and heatwaves; Rogers et al 2021, Singh et al 2021), have enabled an ever wider array of risk scenarios to be considered with sophistication. However, there remains a lack of systematic and cross-scale overviews of potential hazard interaction.…”