Climate science: Coasts more vulnerable to sea-level rise than previously thought

The global coastline is three times more vulnerable to sea-level rise and coastal flooding than previous estimates, suggests a modelling study in Nature Communications.

Scott Kulp and Benjamin Strauss used a new digital elevation model, called CoastalDEM, to assess global population exposures to extreme coastal waters. The model uses a neural network that helps to reduce the vertical bias of previous models. The authors found that their model estimates a global total of 110 million people living on land below the current high tide line and 250 million on land below current annual flood levels. This is in contrast to previous estimates of 28 million and 65 million respectively.

Using their model, the authors suggest that under a low carbon emissions scenario (greenhouse gas emissions peaking by 2020), 190 million people occupy land that will be below projected sea levels for 2100. In a high emissions scenario (greenhouse gas emissions continue to rise through the 21st century), up to 630 million people globally live on land that will be below projected annual flood levels for the end of the century. They estimate that currently one billion people occupy land less than 10 metres above high tide levels, with 250 million people living less than one metre above high tide.