Climate change: Sea level rise to affect ‘three times more people’

(BBC) – Millions of people will be at risk of coastal flooding from climate-driven sea-level rise later this century.

That’s the conclusion of new research conducted by Climate Central, a US-based non-profit news organisation.

It finds that 190 million people will be living in areas that are projected to be below high-tide lines come 2100.

Today, the group calculates roughly 110 million are presently occupying these lands, protected by walls, levees, and other coastal defences.

The future at-risk total assumes only moderate global warming and therefore limited ocean encroachment.

Climate Central’s investigations, published in the journal Nature Communications, have sought to correct the biases in the elevation datasets previously used to work out how far inland coastlines will be inundated.

Map showing flood risk in Bangkok 2050
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The most famous of these datasets comes from a space shuttle mission.

The Endeavour orbiter used a radar instrument in 2000 to map heights across the globe. This 3D model of the planet has become one of the most used Earth observation datasets in history.

But the Climate Central team, of Scott Kulp and Benjamin Strauss, says it suffers from biases that in places make the land look higher than it really is.

This problem occurs particularly in locations where there is thick vegetation, such as forests; the radar tends to see the tree canopy, not the ground.

Kulp and Strauss used more modern, higher-resolution information from airborne lidar (laser) instruments to train a computer to make corrections to the shuttle’s digital elevation model (DEM).

When this new CoastalDEM is used in tandem with population statistics and the latest forecasts for sea level rise, it becomes apparent that many more people are entering a precarious future.

The improved elevation data finds that even with moderate reductions in greenhouse gas emissions, six Asian countries (China, Bangladesh, India, Vietnam, Indonesia, and Thailand), where 237 million people live today, could face annual coastal flooding threats by 2050. That’s roughly 183 million more than assessments based on prevailing elevation data.

New estimate versus old estimate

  1. China – 93 million vs 29 million
  2. Bangladesh – 42 million vs 5 million
  3. India – 36 million vs 5 million
  4. Vietnam – 31 million vs 9 million
  5. Indonesia – 23 million vs 5 million
  6. Thailand – 12 million vs 1 million