Compound interest

What happens when disaster builds on disaster

Climate change will bring hotter weather and rising seas, but what it means for natural disasters such as floods and fires is less clear.

Part of the difficulty is that such catastrophes are often “compound events” in which multiple factors combine to wreak havoc.

Heavy rain will cause worse flooding if dams are already full, for instance, and a heatwave is more likely to spark bushfires if it comes after a drought.

“It’s sequences of events and combinations of events that really cause trouble,” says Andy Pitman of the University of NSW.

“We might be ready for one 47-degree day but when it’s followed by another and another our systems start to break down.”

In 2017, Andy was one of a dozen researchers from Australia, Europe and the US who met in Switzerland to work out an approach to understanding compound events and their effects. It wasn’t just climate scientists—compound events interest the likes of insurance analysts and flood engineers as well, who need to understand and prepare for the risks of the future.

That group has now grown into a European-funded project called DAMOCLES, led by Jakob Zscheischler of the University of Bern and Bart van den Hurk of the Royal Netherlands Meteorological Institute.

“We want to build up a network of researchers on compound events,” says Jakob. “It is hard even to know which combinations of climate variables have the potential to cause large impacts.”

The goal is first to understand what combinations of factors can lead to devastating events, and then to find out how often and when those dangerous combinations are likely to occur as the climate changes.

“We’ll see a lot of work in this area,” says Andy. “It really connects climate science with risk and insurance and infrastructure. This is where the rubber hits the road.”

Banner image credit: Alois_Wonaschuetz