Climate Change: Flood Losses in Major Cities Could be Over $50 Billion by 2050

It turns out that climate change is a lot more expensive than we may have given it credit for. As temperatures warm and sea levels rise, there's expected to be more than a nine-fold increase in the global risk of floods in large port cities. This, in turn, could cost us more than $50 billion by 2050.

In order to assess the risk of flooding, the researchers examined 136 of the world's largest coastal cities, taking into account existing coastal protections. They also examined the cities ranked most "at risk" today, as measured by the annual average losses due to floods. These included Guangzhou, Miami, New York, New Orleans, Mumbai, Nagoya, Boston, Tampa-St. Petersburg, Vancouver and others.

So what did they find? It turns out that certain U.S. cities are most at risk. Due to their high wealth and low protection level, Miami, New York and New Orleans are responsible for 31 percent of the losses across the 136 cities. That's a huge chunk of the overall cost of floods.

Yet estimating how at risk certain cities were didn't tell researchers how they might be impacted in the future. In order to find that out, scientists assumed that mean sea level, including contributions from melting ice sheets, will rise .2 to .4 meters by 2050. In addition, about a quarter of the 136 cities are in deltas, which means that they're exposed to local subsidence and local sea level change, especially where groundwater extraction accelerations the natural processes.

By taking all of these factors into account, the scientists found that average global flood losses, which were estimated to be about $6 billion per year in 2005, could rise to $52 billion by 2050. This would have drastic impacts on the global economy.

"This work shows that flood risk is rising in coastal cities globally due to a range of factors, including sea level rise," said Robert Nicholls, one of the researchers, in a news release. "Hence there is a pressing need to start planning how to manage flood risk now."

The findings could allow cities to better prepare for future flood risks that are set to swamp areas in 2050. Yet even with the forewarning, the magnitude of losses is set to increase. Better evacuation plans and flood defense will be crucial to help mitigate these losses as sea levels continue to rise.

The findings are published in the journal Nature Climate Change.