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Warming risks listed by population, costs

Image: Mumbai
This view of a Hindu celebration on Sept. 25 reflects the fact that Mumbai, India, has coastline on the Arabian Sea — a geographic attribute that makes it vulnerable to flooding if seas continue to rise.Pal Pillai / AFP-Getty Images file
/ Source: staff and news service reports

The number of people threatened by coastal flooding due to climate change could more than triple by 2070 and the value of exposed property could balloon to $35 trillion, according to a report released Tuesday by the Organization for Economic Cooperation and Development.

The Paris-based OECD, an international non-governmental organization that collects and studies economic statistics and social data, called for quick action on coastal defenses for cities at risk, saying it can take 30 years to build defenses for vulnerable cities.

"Climate change is already happening, and concerted action is needed now to prevent its worst impacts," OECD Secretary-General Angel Gurria said in a statement. "A range of economic policy options is available and political commitment is needed to implement them."

About 150 million people could be exposed to a "1-in-100 year" flooding event by 2070 — up from 40 million now at risk, according to the report. The "1-in-100-year" scenario, which was used because it is a commonly accepted risk assessment standard, also assumed a mean rise in sea level of a half-meter (1.6 feet) by 2070.

The study estimated the financial impact of such a scenario at $35 trillion, compared to $3 trillion today.

Cities listed The report also listed cities most likely to be impacted in terms of population and cost, focusing on 136 port cities around the world.

Calcutta, India, heads the list of the top 10 cities at risk in 2070 in terms of population exposure, with India's Mumbai, or Bombay, second. Miami, Fla., in ninth place, was the only city in a developed country on the report's list of the 10 top cities at risk due to population exposure.

The other cities on that list are Dhaka (Bangladesh), Guangzhou (China), Ho Chi Minh City (Vietnam), Shanghai (China), Bangkok (Thailand), Rangoon (Myanmar) and Hai Phong (Vietnam), respectively.

For present-day conditions, the top 10 cities in terms of exposed population are estimated to be Mumbai , Guangzhou, Shanghai, Miami, Ho Chi Minh City, Calcutta, Greater New York, Osaka-Kobe (Japan), Alexandria (Egypt) and New Orleans, respectively.

In terms of the highest value of property and infrastructure assets in 2070, Miami leads that list should a "1-in-100-year" flood occur, the report said, with exposed assets expected to rise from $400 billion today to over $3.5 trillion by 2070.

Rising impact in Asia
The report pointed to the development of Asian "mega-cities," with their soaring populations, as a key factor increasing the risk in coastal flooding.

Indeed, by 2070, eight of the most financially exposed cities were predicted to be in Asia. Guangzhou is the second most exposed city in terms of assets, followed by New York, Calcutta, Shanghai, Mumbai, Tianjin (China), Tokyo (Japan), Hong Kong (China), and Bangkok, respectively.

In terms of assets today, Miami also leads in that category, followed by the greater New York area, New Orleans, Osaka-Kobe, Tokyo, Amsterdam (Netherlands), Rotterdam (Netherlands), Nagoya (Japan), Tampa-St Petersburg and Virginia Beach.

"The policy implications of this report are clear," the OECD said in an introduction, "The benefits of climate change policies — both global mitigation and local adaptation at the city-scale — are potentially great."

As for the cost of inaction, the report states that "(Hurricane) Katrina and New Orleans demonstrates how significant these consequences might be — 1,500 deaths, evacuation of 700,000 people, with hundreds of thousands still displaced two years on, massive flood damage from which recovery is still ongoing, and the global shock to the oil price.

"New Orleans may never fully recover and another major hurricane landfall could trigger further decline or even total abandonment," the report adds. "Given the large and growing concentration of people and assets in port city locations, and the importance of global trade, failure to develop effective adaptation strategies would inevitably have not just local but also large national and even wider economic consequences."

The report was the first in a series by the OECD looking at the economic impact of climate change on cities.

The full report is online at