Flood exposures rise well beyond climate-driven risks: Marsh flood index

Asia Pacific shows both the greatest risk of flooding today amongst developed market regions and the greatest added flooding risks from climate change, but even milder increases in hazards in Europe and North America render potentially devastating increases in the count of people and assets at risk, the  Marsh McLennan Flood Risk Index 2.0 has shown.

“Climate change, economic and demographic trends, and a chronic shortfall in investment in resilience are combining to drive risk higher,” authors reported. “The Index shows that a 3. 5 °C warming would lead to a dramatic increase in flood risk globally, and that even limiting temperature rise to 1.5 or 2 °C would substantially worsen the threat of flooding.”

Amongst developed regions, the overall flood hazards are focused disproportionately on Asia-Pacific and the region suffers more flood risk than Europe or North America as temperatures rise under climate change scenarios, the data set indicates. River, rainfall and coastal flooding all increase as a hazard across scenarios in east Asia and the Pacific.

Australia would be amongst the top four to suffer in the extreme climate scenario on a notable increase in its rainfall flooding hazard reading. Some 30% of the population and 28% of economic assets are currently at risk, and a 2 °C warming could increase those levels to 49% and 52%, respectively, authors call out. New Zealand suffers a huge rise in exposure for only moderate increases in flood threats. Japan, with above-average risk levels today focused on rainfall-flooding, doesn’t suffer worsening risks as temperatures rise. Exposure indexes match those for Australia.

European overall hazard index levels appear moderate at a 4 on the Marsh ten-point scale and appear comparably stable on moderate rises in average temperature, but those readings hide some significant vulnerabilities.

Beyond more obvious threats to the low countries or mountain river flooding, coastal flooding risks top the charts already today for Germany and look uncommonly elevated for its northern Europe neighbours Denmark, Poland and France. Those coastal threats largely rise with temperatures. D Across Europe, Poland, Estonia and Hungary face the strongest rise in hazard index levels with the rise in temperatures.

But those relatively small rise in hazards spell out considerably more significant increases on the index of human and economic exposures, the Marsh index data shows. The average reading on Marsh’s exposure index for main European countries is ca 50% above the increase in APAC.

On the extreme scenario of a 3.5 degree increase in average temperatures, Norway would go from a 1 to a 7 on the Marsh 10-point index of exposures. Finland and Switzerland are amongst companies suffering a 5-point increase of their exposure index on the extreme climate scenario.

In Germany, 6% of the population and 6% of economic assets are currently at risk, while in a 2 °C scenario, 16% of people and 17% of assets would be threatened by flooding.

North America, with an overall hazard threat index today to match Europe but with call-out elevated readings for select coastal and river threats in the United States, appears to face a surprisingly mild run-up in hazard risks as temperatures rise. Canada can take another 3.5 ℃ without anything but fractional changes in its Marsh hazard index while the US.

But the US and Canada, like elsewhere, can put a lot of people and assets at risk by allowing for even those moderate run-ups in hazards, the index data show. Overall exposure index levels rise 5 points for Canada and 4 points for the United States on the extreme 3.5-degree scenario.

In the U.S., 11% of the population and 11% economic assets are currently exposed to flooding. In a 2 °C scenario, these percentages will increase to 24% and 27%, respectively, authors noted.