An Actual Space Laser Shows How Devastating Sea Level Rise May Be

By 2100, scientists estimate, at least 400 million people could live in high-risk areas

Water from the Atlantic Ocean washes over East Atlantic Avenue in Ocean City, N.J. February 28, 2019.Ron Tarver/Philly.Com/ZUMA

This story was originally published by Wired and is reproduced here as part of the Climate Desk collaboration.

An actual space laser is cruising 300 miles above your head right now. Launched in 2018, NASA’s ICESat-2 satellite packs a lidar instrument, the same kind of technology that allows self-driving cars to see in three dimensions by spraying lasers around themselves as they roll down the street and analyzing the light that bounces back. But instead of mapping a road, ICESat-2 measures the elevation of Earth’s surface with extreme accuracy.

Although this space laser means you no harm, it does portend catastrophe. Today in the journal Nature Communications, scientists describe how they used ICESat-2’s new lidar data to map the planet’s land that’s less than 2 meters above sea level, which makes it vulnerable to the creep of sea level rise. Marrying this data with population figures, they calculated that 267 million people currently live in these at-risk areas. Assuming a sea level rise of 1 meter by the year 2100, they project that 410 million people will ultimately live in an affected zone. Asian countries like Bangladesh and Indonesia are particularly vulnerable, but the United States and Europe will also have no shortage of at-risk populations.

“We strongly believe that if the world is going to be able to deal with sea level rise and to conserve nature in coastal zones—that’s an important aspect—elevation must be known,” says study lead author Aljosja Hooijer, a flood risk expert at the National University of Singapore and Deltares, a research institute in the Netherlands.

The paper’s estimates, Hooijer stresses, are conservative on many levels. For one thing, they did it without factoring in explosive population growth in the world’s cities, because of the uncertainties involved in calculating where people will ultimately move. Currently, 55 percent of the planet’s population lives in urban areas, which the United Nations projects will rise to 68 percent by 2050. But this won’t play out evenly—the populations of certain cities may rise faster than others, or even decline.

“The work fills a very big gap that we have at the moment,” says Arizona State University geophysicist Manoochehr Shirzaei, who studies sea level rise but wasn’t involved in this new research. Scientists have good models of sea level rise, Shirzaei adds, “but when you want to quantify the flood risk, you need to know the elevation as well. And that’s a big unknown.”

 
 
 
There’s another problem: In addition to dealing with seawater encroaching on their shores, some cities are also sinking. Land subsidence is a phenomenon in which the ground compacts, usually due to the over-extraction of groundwater. Coastal cities are particularly prone to subsidence because of their geology, as urban centers have historically popped up where rivers meet the sea. Over the millennia, a river would have deposited layer upon layer of clay, and the city would have grown on top of it. But as the metropolis taps into the underlying aquifer, this clay collapses like an empty water bottle, and the city can go along with it. The more an urban center grows, the more people it needs to hydrate, which increases the rate and severity of subsidence.
 
Hooijer’s modeling does take subsidence into account, but it uses a uniform rate of elevation loss—half a centimeter per year—across the world instead of calculating the rate for each coastline on its own. That wouldn’t be feasible. Still, researchers know that some areas are slumping much faster than that: In parts of Jakarta, for instance, the land is sinking by up to 10 inches a year. By 2050, 95 percent of north Jakarta could be underwater, because the land’s elevation is decreasing while sea levels are increasing. The problem is so bad that Indonesia is planning on moving its capital out of the city.

But not all metropolises have come to terms with the subsidence crisis. “Some governments have not admitted to it—that it’s a problem,” says Hooijer. “If you want to make policymakers buy this, you have to be a bit on the conservative side. So we decided to go for a uniform subsidence rate.”

A “huge challenge” is to make sure short-term interventions after disasters like hurricanes Katrina and Sandy, “fit into a long-term planning strategy.”

This new modeling is also conservative in that it considers sea level rise but not storm surges, which is the sudden rise in water level during a hurricane or tropical storm. Ever more powerful cyclones will push ever more water ashore. While these temporary surges aren’t the same kind of severe, long-term threat as sea level rise that can overtake a metropolis, “a major storm surge can happen tomorrow, having devastating impacts on communities, but also triggering interventions by the government,” writes climate scientist Jeroen Aerts of Vrije Universiteit Amsterdam in an email to WIRED. “A huge challenge is to make sure these ‘short-term interventions’ after major disasters—Hurricanes Katrina, Sandy, Harvey, etc.—fit into a long-term planning strategy anticipating sea level rise. Unfortunately, this longer-term perspective is often missing.” (Aerts studies sea level rise but wasn’t involved in this new work.)

This new data is meant to provide that perspective. But a shortcoming, says Shirzaei of Arizona State University, is that with a resolution of 5 kilometers (about 3 miles), the data collected from orbit is quite coarse compared to what you’d get from lidar taken from a plane or drone. “Those lidar data have a resolution of 5 or 10 centimeters,” Shirzaei says. “The quality is just amazing.”

But the two sources of data could actually work in concert, says Shirzaei. You could use the satellite lidar to identify particularly vulnerable areas—according to this study, places like Bangladesh and Indonesia—then deploy a plane to map the coast in finer detail.

This kind of data could show which coastal areas could be safely fortified against rising tides, and which are now too dangerous for habitation. Texas, for instance, is considering building a $26 billion barrier to hold back the sea near Houston. In other places, it might make more sense to elevate structures to adapt to sea level rise, Shirzaei adds.

But sometimes an engineering solution just won’t be possible. “Some of the adaptation strategies could be that we just relocate the entire community, because for some reason we cannot defend them using in-place structures like sea walls,” says Shirzaei. This is known as managed retreat, and it’s already happening in some cities. San Francisco, for instance, is giving up part of a coastal highway by replacing two lanes with a trail so the land can better hold back rising waters.

Now, NASA’s orbiting space laser might help policymakers make informed decisions about whether it’s safer to stay or go.

More Mother Jones reporting on Climate Desk

WE'LL BE BLUNT

It is astonishingly hard keeping a newsroom afloat these days, and we need to raise $253,000 in online donations quickly, by October 7.

The short of it: Last year, we had to cut $1 million from our budget so we could have any chance of breaking even by the time our fiscal year ended in June. And despite a huge rally from so many of you leading up to the deadline, we still came up a bit short on the whole. We can’t let that happen again. We have no wiggle room to begin with, and now we have a hole to dig out of.

Readers also told us to just give it to you straight when we need to ask for your support, and seeing how matter-of-factly explaining our inner workings, our challenges and finances, can bring more of you in has been a real silver lining. So our online membership lead, Brian, lays it all out for you in his personal, insider account (that literally puts his skin in the game!) of how urgent things are right now.

The upshot: Being able to rally $253,000 in donations over these next few weeks is vitally important simply because it is the number that keeps us right on track, helping make sure we don't end up with a bigger gap than can be filled again, helping us avoid any significant (and knowable) cash-flow crunches for now. We used to be more nonchalant about coming up short this time of year, thinking we can make it by the time June rolls around. Not anymore.

Because the in-depth journalism on underreported beats and unique perspectives on the daily news you turn to Mother Jones for is only possible because readers fund us. Corporations and powerful people with deep pockets will never sustain the type of journalism we exist to do. The only investors who won’t let independent, investigative journalism down are the people who actually care about its future—you.

And we need readers to show up for us big time—again.

Getting just 10 percent of the people who care enough about our work to be reading this blurb to part with a few bucks would be utterly transformative for us, and that's very much what we need to keep charging hard in this financially uncertain, high-stakes year.

If you can right now, please support the journalism you get from Mother Jones with a donation at whatever amount works for you. And please do it now, before you move on to whatever you're about to do next and think maybe you'll get to it later, because every gift matters and we really need to see a strong response if we're going to raise the $253,000 we need in less than three weeks.

payment methods

WE'LL BE BLUNT

It is astonishingly hard keeping a newsroom afloat these days, and we need to raise $253,000 in online donations quickly, by October 7.

The short of it: Last year, we had to cut $1 million from our budget so we could have any chance of breaking even by the time our fiscal year ended in June. And despite a huge rally from so many of you leading up to the deadline, we still came up a bit short on the whole. We can’t let that happen again. We have no wiggle room to begin with, and now we have a hole to dig out of.

Readers also told us to just give it to you straight when we need to ask for your support, and seeing how matter-of-factly explaining our inner workings, our challenges and finances, can bring more of you in has been a real silver lining. So our online membership lead, Brian, lays it all out for you in his personal, insider account (that literally puts his skin in the game!) of how urgent things are right now.

The upshot: Being able to rally $253,000 in donations over these next few weeks is vitally important simply because it is the number that keeps us right on track, helping make sure we don't end up with a bigger gap than can be filled again, helping us avoid any significant (and knowable) cash-flow crunches for now. We used to be more nonchalant about coming up short this time of year, thinking we can make it by the time June rolls around. Not anymore.

Because the in-depth journalism on underreported beats and unique perspectives on the daily news you turn to Mother Jones for is only possible because readers fund us. Corporations and powerful people with deep pockets will never sustain the type of journalism we exist to do. The only investors who won’t let independent, investigative journalism down are the people who actually care about its future—you.

And we need readers to show up for us big time—again.

Getting just 10 percent of the people who care enough about our work to be reading this blurb to part with a few bucks would be utterly transformative for us, and that's very much what we need to keep charging hard in this financially uncertain, high-stakes year.

If you can right now, please support the journalism you get from Mother Jones with a donation at whatever amount works for you. And please do it now, before you move on to whatever you're about to do next and think maybe you'll get to it later, because every gift matters and we really need to see a strong response if we're going to raise the $253,000 we need in less than three weeks.

payment methods

We Recommend

Latest

Sign up for our free newsletter

Subscribe to the Mother Jones Daily to have our top stories delivered directly to your inbox.

Get our award-winning magazine

Save big on a full year of investigations, ideas, and insights.

Subscribe

Support our journalism

Help Mother Jones' reporters dig deep with a tax-deductible donation.

Donate