Multi-hazard dependencies can increase or decrease risk

Abstract:

The interplay among natural hazards affects risk globally. Over meteorological timescales (hours to weeks), hazards like wind and precipitation extremes can combine to exacerbate total risk. However, infrastructure operators, government agencies, (re)insurance and health services are also interested in aggregated risk over climatological timescales (seasonal to annual). Using Australia and Great Britain (GB) as examples we illustrate that, from this perspective, hazards can be influenced by modes of atmospheric variability in ways that reduce the likelihood of some hazard combinations, thereby moderating tail-end (worst-case) compound risk. In other words, purely pairwise views of a multi-hazard environment that target instances where risk is exacerbated might overestimate worst-case risk. We highlight this aspect of the need for a broader and more holistic view of multi-hazard risks.