Because it conjures up a tangible, visible image in the human mind, the prospect of an uncontrolled global sea rise is one of the most benumbing examples of the consequences of man-made climate change. In Al Gore’s now-iconic 2006 documentary film, An Inconvenient Truth, the consequences of rising seas caused by the melting of the polar ice caps and the Greenland ice sheet were vividly depicted based on satellite imagery. Projecting the encroachment of ocean waters throughout the low-lying state of Florida, the impact of those unforgettable images far exceeded that of any abstract studies, and demonstrated the dire nature of what is now almost certain to befall the world during the lifetimes of today’s children.
Unfortunately, it turns out that those alarming assessments were inaccurate: The consequences of rising sea levels look to be even more devastating than previously predicted.
Prior studies that estimated the degree of global sea level rise based on current rates of man-made greenhouse gas emissions all suffered from a simple but crucial methodological error, according to a new study published in the open-access journal Nature Communications on Oct. 29.
The error was in estimating the impact of sea rise based primarily on 3-D satellite imagery from NASA, which led scientists to erroneously establish “the planet’s upper surfaces—such as treetops and tall buildings,” as ground level. This, as New York magazine’s Intelligencer summarizes, was the elevation data that scientists generally relied on when estimating the degree of incursion that rising seas would represent. Scientists Scott A. Kulp and Benjamin H. Strauss, in affiliation with Princeton University and the organization Climate Central, recently discovered and corrected for this error and, with the assistance of artificial intelligence technology, were able to correct prior estimates.
When extrapolated to show the effect of sea rise on human populations, the data now indicate “that many of the world’s coastlines are far lower than has been generally known.” This means that “sea level rise could affect hundreds of millions of more people in the coming decades” than was already feared. That’s a three- to four-fold increase over estimates based on the erroneous NASA data.
In terms of actual numbers, by 2050, as many as 150 million to 340 million people living below annual high-tide or flood levels could be subject to displacement by higher sea levels, depending on which scenario—“optimistic” (reflecting lower rates of continued greenhouse gas emissions) or “pessimistic” (reflecting higher rates of such emissions)—is considered. The projections for 2100 roughly double these numbers, if that can be imagined.
Southern and southeastern Asia will be the areas first and most severely impacted—Bangkok, Thailand, and much of southern Vietnam, for example, will disappear by 2050, according to these estimates—but these regions are hardly alone. The study indicates that Brazil and the United Kingdom could permanently lose land to the rising waters by the end of this century. Sooner than that, in 2050, Kulp and Strauss estimate, over 3.6 million people in Great Britain alone could face annual flooding. Additionally, the study predicts that “even in the U.S.,” the sea rise impact could lead to climate-driven migration from the coastlines.
In practical terms, however, it is necessary to account for human migration, as well as the fact that the population of the world is expected to increase by two billion people by 2050. Because the interiors of affected countries will also be affected by increased warmth, an influx of refugees toward the exact same cities impacted by sea rise is expected. Large inland populations attempting to escape the consequences of increasing temperatures will be greeted not by the cooling waters of the coastline—instead, they’ll find floods and less coastal land than ever.
Between now and 2050, the percentage of the global population living in urban areas is expected to increase from 55 to 68 percent. And climate change could accelerate migration from rural areas to coastal cities as warming devastates many of the world’s agricultural regions. In other words, many coastal cities in the developing world are likely to see influxes of climate refugees, just as rising tides begin displacing their existing populations.
Widespread construction of massive sea walls around affected cities could be the only way to save low-lying cities from the encroachment of the oceans. However, whether the resources and political will necessary to undertake such an effort will be available is, at best, doubtful. As New York’s Eric Levitz notes, the social transformations required to relocate these populations will be enormous.
If the Princeton researchers’ projections are correct, averting mass death and suffering in the coming decades will require not only rapidly reducing carbon emissions and ramping up construction of seawalls and other fortifications but also facilitating mass migrations away from low-lying cities and islands and toward higher ground.
The real-world impact of these estimated consequences of climate change on actual low-lying cities is also vividly explored by The New York Times.
“The need for coastal defences and higher planning for higher seas is much greater than we thought if we are to avoid economic harm and instability,” Climate Central CEO Strauss said. “The silver lining to our research: although many more people are threatened than we thought, the benefits of action are greater.”
For his part, Donald Trump confirmed this week that the United States would be exiting the Paris climate accord, with the process beginning as early as Nov. 4. Surrounded by men in hardhats at a Pittsburgh conference on energy, Trump railed against the agreement, and insisted that his fossil fuel-friendly policies have allowed the U.S. to become an energy superpower. At 73, Trump most likely will not be around in 2050 to see the end result of his handiwork.
Unfortunately, many of us will be.