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The worst effects of sea level rise will hit earlier than expected

Current models of sea level rise suggest that the most widespread effects will occur several meters after sea level rise. But a new study finds that the largest increases in flooding will occur after the first 2 meters (6.6 feet) of sea level rise, covering more than twice the land area predicted by older elevation models.

The study, published in Earth’s Future, used high-resolution measurements of Earth’s elevation from NASA’s ICESat-2 lidar satellite, launched in 2018, to improve models of sea level and flooding. less accurate.


“Radar is unable to fully penetrate vegetation, and thus overestimates surface elevation,” said Ronald Vernemen, a researcher at Dutch research firm Data for Sustainability. Many coastal areas are lower than scientists thought.

The biggest impacts are sea level rise

Underestimating land elevation means that coastal communities have less time to prepare for sea level rise than expected, with the largest effects of sea level rise occurring earlier than previously thought. After those first few meters of sea level rise, the rate of land area decreases.


Vernemin, who works on flood protection and spatial planning consulting projects, began using these more accurate measurements of ground elevation when he realized that current ground elevation estimates were not suitable for estimating coastal flood risk.

Using new measurements of Earth’s elevation, Vernemin and co-author Aljosja Hooijer found that coastal areas lie much lower than suggested by the older radar data.

A sea level height of 2 meters would cover 2.4 times the land

Analyzes of the new lidar-based elevation model revealed that a sea level rise of 2 meters would cover up to 2.4 times the land area as observed through radar-based elevation models.

For example, lidar data indicates that a sea-level rise of 2 meters (6.6 feet) could put most of Bangkok and its 10 million residents below sea level, while older data indicated that Bangkok would still be well above sea level. The sea is below the same level as the sea level rise.

In total, after rising 2 meters (6.6 ft) from sea level, Ferenmen and Hueger estimate that another 240 million people would live below mean sea level. After rising 3 and 4 meters (9.8 and 13 ft) from sea level, that number increased by 140 million and another 116 million, respectively.

Amsterdam and New Orleans are recent examples

According to Frenmin, cities below sea level in the future may not necessarily be submerged because dams and pumping stations can protect some areas from rising seas; Amsterdam and New Orleans are recent examples of this. These protection measures can be costly and take decades to implement. If vulnerable communities want to mitigate the most damage, they must act before the seas rise those first few metres.



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