New Sea Level Impacts Estimate is Dire

October 30, 2019

Associated Press via CTV:

WASHINGTON — The number of people threatened by climate change-triggered flooding is about three times higher than previously thought, a new study says. But it’s not because of more water.

It’s because the land, especially in Asia and the developing world, is several feet lower than what space-based radar has calculated, according to a study in the journal Nature Communications Tuesday.

So instead of 80 million people living in low-lying areas that would flood annually by 2050 as the world warms, this new study finds the population at risk is closer to 300 million people.


And if emissions of heat-trapping gases continue unabated and Antarctic ice melts more in a worst-case scenario, around 500 million people could be at risk by the end of the century, according to the study by Climate Central , a New Jersey based non-profit of scientists and journalists.

Space-based radar says 170 million are at risk in that scenario.

For big picture global mapping of flooding threats, the go-to technology for elevation is NASA’s Shuttle Radar Topography Mission . But that doesn’t accurately show ground, instead mistaking rooftops and tree canopies for ground with an average error of 6.5 feet (2 metres), said Climate Central chief executive officer Ben Strauss, a scientist who studies sea level rise.


For the United States, much of Europe and Australia, this is not a problem because those areas use airborne lidar radar, which is more accurate about true elevation. But in flood prone Asia and other places that’s not an option, Strauss said.

So Climate Central used the shuttle radar, artificial intelligence and 23 different variables to create a computer model that is more accurate in globally mapping elevation, Strauss said. They then tested it against the airplane-generated data in the United States and Australia and found this computer model was accurate, he said.

“This is a far greater problem than we understood,” Strauss said. “Far more people live in risky places today than we thought and the problem only multiplies in the future.”

New York Times:

Southern Vietnam could all but disappear.

The first map shows earlier expectations of submerged land by 2050. But the new outlook, the second map, indicates that the bottom part of the country will be underwater at high tide.

More than 20 million people in Vietnam, almost one-quarter of the population, live on land that will be inundated.

Much of Ho Chi Minh City, the nation’s economic center, would disappear with it, according to the research, which was produced by Climate Central, a science organization based in New Jersey, and published in the journal Nature Communications. The projections don’t account for future population growth or land lost to coastal erosion.


Standard elevation measurements using satellites struggle to differentiate the true ground level from the tops of trees or buildings, said Scott A. Kulp, a researcher at Climate Central and one of the paper’s authors. So he and Benjamin Strauss, Climate Central’s chief executive, used artificial intelligence to determine the error rate and correct for it.

In Thailand, more than 10 percent of citizens now live on land that is likely to be inundated by 2050, compared with just 1 percent according to the earlier technique. The political and commercial capital, Bangkok, is particularly imperiled.

Climate change will put pressure on cities in multiple ways, said Loretta Hieber Girardet, a Bangkok resident and United Nations disaster risk-reduction official. Even as global warming floods more places, it will also push poor farmers off the land to seek work in cities.

“It is a dire formula,” she said.

In Shanghai, one of Asia’s most important economic engines, water threatens to consume the heart of the city and many other cities around it.

The findings don’t have to spell the end of those areas. The new data shows that 110 million people already live in places that are below the high tide line, which Mr. Strauss attributes to protective measures like seawalls and other barriers. Cities must invest vastly greater sums in such defenses, Mr. Strauss said, and they must do it quickly.

But even if that investment happens, defensive measures can go only so far. Mr. Strauss offered the example of New Orleans, a city below sea level that was devastated in 2005 when its extensive levees and other protections failed during Hurricane Katrina. “How deep a bowl do we want to live in”? he asked.

Below, a recent video features globally recognized experts on sea level rise.

6 Responses to “New Sea Level Impacts Estimate is Dire”

  1. rhymeswithgoalie Says:

    People on the Nile delta already know this, but there’s a major difference between the Nile River flooding (which has supported agriculture for thousands of years) and salty flooding from the Mediterranean. At the very least farmers and herders have to switch to salt-tolerant plants, but they’d have to do it before the quickly rising sea level washes away the soil when the freshwater plant life dies.

  2. indy222 Says:

    My students first told me of this, yesterday… I checked it out and yeah – this is really bad. I’m waiting to see if the media picks up on this, because it’s a very big deal. What I’m amazed by, is that a correction for the fact this method only gives the elevation of the buildings and vegetation, not the ground, took this long to figure out.

  3. terry123a Says:

    NOAA ocean rise trends has one station in Egypt, Alexandria which stops around 2005. From about 1960 to 2005 one gets wide swings but the actual rise over that time is about zero as it stays at about 7.05 meters I suspect the site suffers from land subsidence problems which is probable as it sits at the end of the nile on a wide delta plain. If one looks at say Relative Sea Level Trend 290-011 Positioning, Greece, essentially zero ocean rise since since 1970 to date with again large yearly swings. The ocean may be rising but data shows it is not which leads one to wonder if the new super dupper model for ocean rise is simply wrong. I cannot find any explanation of why the model simply ignores contrary data.

    Many cities are built on coastal plains which subside when one pumps out the water holding them up. Jakarta is an example in Asia. Our eastern seaboard has that same problem along with subsidence from continental rebound.

    A whole lot of people live in floodplains barely above sea level. The population is exploding in a lot of third world countries and the people living on those flood plains is doubling every 30 years or so. That increase is the actual problem.

    • rhymeswithgoalie Says:

      Check out the non-subsiding City of Miami* increasing its rate of flooding.

      Yes, people measuring sea level know about subsidence from extraction (oil or water) and/or accelerating deprivation of sediment (e.g., industrially-channeled coastlines of Louisiana and east Texas), and natural unlithified slumping.

      The planet’s oceans are measurably gaining heat, therefore expanding the overall ocean volume. Old land ice is melting off into the sea, therefore expanding the overall ocean volume. Now, while our warming troposphere can hold more water vapor, it is not holding as many extra gigatons as are melting off of Greenland and the WAIS.
      *The City of Miami, built on limestone, is very different from the City of Miami Beach, built on barrier islands.

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