Climate change and population migration could put an additional 52 million people in the path of coastal flooding from storm surges in the next century, according to a report from the Center for Global Development.
The report looks specifically at the impact of storm surges on the land, populations and economies of 84 developing countries and 577 coastal cities within them.
The report found that impacts ranged widely by region — with more than 25 percent of the additionally vulnerable population being concentrated in three cities: Manila, Philippines; Alexandria, Egypt; and Lagos, Nigeria. In Manila alone, 3.4 million more people are expected to be vulnerable to storm surge flooding, the report says.
“Normally, you’ll find a lot of studies that are sort of on a case-by-case type of situation,” said Carlos Perez, a senior analyst at the International Research Institute for Climate and Society, regarding studies on future storm surges, “whereas this tried to be comprehensive and tries to includes lots of countries.”
Climate change is expected to bring more frequent and intense storms, and as a result, higher surges that will cause more damage because they can move farther inland, the report says. Meanwhile, population growth and migration are bringing more people to coastal areas.
“During the 21st century, rising storm surges and growing populations threaten to collide in disasters of unprecedented size,” the authors wrote.
This study focused on the largest storm surges, namely, the ones that happen once every 100 years.
“It’s trying to see how the statistics are going to change of the likelihood that you’re going to get hit with a doozy,” said Stephen Schneider, a climate scientist at Stanford University. “You worry about the worst case, because the worst case is what gets you the most damage,” he added, saying that 95 percent of the worst damage happens in the 5 percent of storms that are the strongest.
Overall, the largest increases in population that would be affected are expected to be in the Middle East and North Africa. Economic impacts from the changing storm surges, on the other hand, are expected to be worst in East Asia, the report says. And that is distinct from the projection that the most land will be additionally affected in Latin America and the Caribbean.
“In light of the huge asymmetries in our country- and city-level results,” the authors wrote, “we believe that careful targeting of international assistance will be essential.”
In the study, researchers combined projections of sea level rise, storm surge height and land subsidence with data on population, economy and other factors, like location of agricultural lands or wetlands.
The authors acknowledge that limitations to the study include their use of a uniform — 10 percent — increase in the height of storm surges as an assumption, while they say that in reality, how storm surges change with climate change will vary across regions. The study also did not account for coastal erosion or coastal protection measures, like dikes, or examine impacts on small island nations.
Overall, Perez said, “It’s a pretty innovative approach. They’ve been quite thorough in their analysis … and they’re conservative in their estimates. They’re not exaggerating.”