Climate-change-driven flooding could endanger 200 million people—in 30 years

Rising tides and storm surges will devastate economies and communities around the globe, if we don't dramatically cut greenhouse-gas emissions and bolster shoreline protection.

By the end of the century, increased coastal flooding driven by swelling ocean levels will endanger more than 250 million people and nearly $13 trillion worth of coastal buildings and infrastructure, according to a new study led by researchers at the University of Melbourne. And that's under a relatively optimistic climate-change scenario.

The findings: The research is based on modeling of tides, storm surges, wave patterns, and regional sea level rise, under various scenarios of greenhouse-gas emissions from the UN's climate panel. The $13 trillion figure assumes no steps are taken to shore up coastlines with seawalls or other protections, and that carbon dioxide pollution peaks around 2040 and begins falling thereafter-a moderate emissions scenario.

The worst case: Under a scenario in which emissions continue to rise unchecked through the century, coastal flooding would threaten nearly 290 million people and more than $14 trillion in coastal assets-or 20% of global GDP. (Some climate researchers, however, argue that this RCP8.5" scenario is increasingly implausible given the steps some nations have already taken to flatten emissions.)

Before then: In just 30 years, nearly 204 million people and $11 billion in assets could be exposed to coastal flooding, up 16% and 14% from today, respectively, under the moderate scenario.

Northern Australia, northwestern Europe, southeastern China, the US East Coast, Bangladesh, and several states in India will all be at particularly high risk of frequent and extensive flooding, the study found.