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Real space the laser is crossing 300 miles above your head right now. NASA’s ICESat-2 satellite, launched in 2018, incorporates a lidar tool, the same technology that allows drivers to see in three dimensions, by throwing cars down the street and scanning the light that is bouncing backwards by laser-cutting cars. But instead of mapping a road, ICESat-2 accurately measures the altitude of the Earth’s surface.
Although this space laser does no harm to you, it does predicting disaster. In the magazine today Nature Communications, scientists describe how they used the new ICESat-2 lidar data to map lands on the planet less than 2 meters above sea level, which makes them vulnerable to sea level rise. Combined with these population figures, it is estimated that 267 million people currently live in these risk areas. Assuming a sea level rise by 2100, 410 million people are expected to live in an affected area. Asian countries like Bangladesh and Indonesia are particularly vulnerable, but the United States and Europe will also not be short of endangered populations.
“We strongly believe that if the world is to be able to cope with rising sea levels and conserve nature in coastal areas – that is an important aspect – altitude must be known,” says author Aljosja Hooijer, a flood risk expert at the National University of Singapore and Deltares, a research institute in the Netherlands.
The paper’s calculations, Hooijer points out, are conservative on many levels. On the one hand, they did without given the explosive population growth in cities around the world, due to the doubts involved in calculating where people will move. Today, 55% of the planet’s population lives in urban areas United Nations projects By 2050 it will rise to 68 percent. But that will not play out in a uniform way; populations in some cities may increase or even decrease faster than others.
“The work fills a huge gap we have at the moment,” says Arizona State University geophysicist Manoochehr Shirzaei. examines sea level rise but was not involved in this new research. Scientists are good models according to sea level rise, Shirzaei adds, “but when you want to quantify the risk of flooding, you also need to know the elevation. And that’s a big unknown. “
Previously, researchers used satellite radar to map elevations. It works on the same principle as the leader, instead of lasers bouncing radars off the ground. “The problem with radar is that it can’t penetrate the vegetation, just a little bit,” Hooijer says. “It gets stuck somewhere between the awning and the surface of the ground, and the elevation measure you get is between.” Lasers, on the other hand, are easily incorporated into vegetation, providing a more accurate measurement. (Maybe you’ll know how scientists use lidar to see through Amazon rainforest trees map ancient ruins hidden below.)
Hooijer found that 72% of the population at risk of flooding will live in the tropics. Only tropical Asia will be at 59 percent of the risk area, because the region is particularly low. “It’s a huge problem for developed countries, Europe and the states,” Hooijer says. “But if you look at the roadmap, who are the people who will suffer the most, and probably the fastest? It’s poor people, especially those who live in underdeveloped areas. It doesn’t get that much attention, which is really a hot spot. And we were amazed by the numbers. ”
There is another problem: in addition to seawater entering their shores, some cities are also sinking. Land subsidence is a phenomenon dense soil, usually excessive extraction of groundwater. Coastal cities tend to sink mainly due to geology, as urban areas have historically been created where rivers meet the sea. Over the millennia, a river would accumulate a layer of clay and the city would grow on it. But when the aquifer below the metropolis enters, that clay falls like an empty water bottle and the city can go with it. The more urban areas grow, the more people need to be hydrated, which increases the rate of sinking and severity.
Hooijer’s modeling takes into account sinking, but uses a uniform elevation rate — half a centimeter a year — instead of calculating the rate for each coast around the world on its own. That would not be feasible. However, researchers know that some areas are sinking much faster than this: In some parts of Jakarta, for example, the earth is sinking. 10 inches a year. By 2050, the percentage of northern Jakarta could be below 95 water due to the altitude of the earth it is declining while sea levels are rising. The problem is so serious that Indonesia intends to take its capital out of the city.
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