Atmospheric Rivers, Derechos And Bomb Cyclones On Insurers’ Radar

Wild and wacky weather events like atmospheric rivers, derechos and bomb cyclones may seem new because of recent media coverage, but they’ve been known and named phenomena for quite some time in the history of meteorology and atmospheric science, speakers said Tuesday at the CatIQ Connect conference.

What’s new is that they appear to be getting worse and more frequent as the climate changes. That means increasingly higher insured damage payouts for Canada’s P&C insurance industry.

For example, a May 2022 derecho -- a fast moving line of thunderstorms with strong winds -- in Ontario and Quebec cost the P&C insurance industry at least $1 billion in claims payouts, while the November 2021 atmospheric rivers in British Columbia cost at least $675 million in insured damage.

When it comes to atmospheric rivers -- which could be described as fire hoses or trains of moisture -- and other weather phenomena, climate change is contributing to increased events.

This in part can be attributed to the Clausius-Clapeyron relation, which says that for every one degree centigrade of warming, the atmosphere can hold at least 7% more moisture, said Steve Bowen, chief science officer with Gallagher Re.