Current models of sea level rise suggest the most widespread impacts will occur after sea level has risen by several meters. A new study using updated models has instead found that the biggest increases of inundation will occur after the first two meters of sea level rise, covering more than twice as much land as older models predicted.
This means that many coastal areas are lower than previously thought, leaving communities with less time to prepare for sea level rise than expected.
The study used data from a NASA satellite that was launched in 2018 to improve sea level rise models. Previous studies relied on radar-based data, which are less precise and overestimate land surface elevation.
Ronald Vernimmen, a researcher at the Dutch research firm Data for Sustainability, started using the more accurate measurements when he realized that existing estimates were not suitable for quantifying flood risk.
Based on the new measurements, the study revealed that coastal areas lie much lower than older data suggested. According to the research, two meters of sea-level rise would cover up to 2.4 times the land area as observed by radar-based elevation models.
For example, a two-meter increase in sea level could put most of Bangkok and its 10 million residents below sea level, while older data suggested that Bangkok would still be largely above sea level.
In total, after two meters of sea level rise, the researchers estimate that 240 million more people will live below sea level. After three and four meters of sea level rise, that number increases by 140 million and by another 116 million, respectively.
There are adaptation measures that can be implemented to avoid devastating impacts. Cities below future sea level could use levees, dikes and pumping stations to protect areas from rising seas. Amsterdam and New Orleans are modern examples of this. However, these measures can be expensive and take decades to implement.
To mitigate as much damage as possible, vulnerable communities must act before the sea rises those first few meters, according to Vernimmen.
The research is published by the American Geophysical Union in the journal Earth s Future.
Check us out on EarthSnap, a free app brought to you by Eric Ralls and Earth.com.