A new study finds that previous estimates of the impact of rising sea levels on coastal communities were far too optimistic, and that as many as three times the number of people as previously estimated will be affected as the waters continue to rise. It's only the latest in a long and growing list of reasons the U.S. needs to resume serious action to address climate change.
As human-caused global warming from greenhouse gases pushes temperatures to unprecedented levels worldwide, sea levels are rising as well, the result of melting ice and warming water, which expands after it warms beyond 4 degrees Celsius. Scientists can calculate how high those sea levels will rise in decades to come, but how it will affect human communities is a trickier question. That requires figuring out how many areas are actually below flood level now and how many people live in those areas — a more complicated task than it might sound like.
A study last month in the journal Nature Communications posits that previous estimates have been grievously low because they're based largely on old data-collection methods that underestimated how much coastal land already sits below flood level. As the study notes, "Translating sea-level projections into potential exposure of population is critical for coastal planning and for assessing the benefits of climate mitigation, as well as the costs of failure to act."
Those costs are already astronomical. Using more current technology, the study estimates that some 110 million people worldwide already live on land below the high-tide line — fully three times as many as previously thought. The number of people facing consistent flooding will expand to 150 million by 2050, the study projects.
That number could double if Antarctic ice melts faster than the most optimistic projections.
Those who dispute the facts regarding human-caused global warming will no doubt try to portray these latest updates as further proof that scientists are wrong because they're always changing their conclusions. In fact, improving the data and honing the conclusions with the help of better information is how good science works. Bad science draws erroneous conclusions from flawed data, such as the anti-vaccination movement's unfounded belief that vaccines cause autism.
The Trump administration and other anti-science critics are fond of saying (generally with zero evidence) that scientists' predictions about the coming effects of global warming are "alarmist." The broad takeaway from the new report is that, if anything, they haven't been alarmist enough. It's telling that the more scientists learn about climate change and its impacts, the worse the future looks. The U.S., once a global leader on the issue, needs to be again. It's a role America can't hope to resume, though, while a stubborn climate-change denier sits in the Oval Office.
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