To slow Earth’s warming, some scientists have proposed pumping tons of tiny light-scattering particles into the upper atmosphere to reflect sunlight back into space. A new analysis suggests that such “geoengineering” might also reduce the number of storm surges as big as the one that swamped New Orleans in the wake of Hurricane Katrina. The team used climate models to assess the effect of injecting various quantities of light-scattering sulfate aerosols into the stratosphere in a scenario where atmospheric concentrations of carbon dioxide reach 650 parts per million in the year 2100. (For comparison, in 2014, average atmospheric concentration of the gas was about 398.5 ppm and had risen about 2.1 ppm each year in the previous decade.) If engineers were to spray about 10 million metric tons of sulfur dioxide droplets into the stratosphere each year between 2020 and 2070, the number of storm surge inundations produced by large hurricanes each year after 2070 drops by about half, the researchers report online today in the Proceedings of the National Academy of Sciences. Much of the reduction in storm surge stems from slowing the rate of sea level rise (cooler Earth = glaciers melting more slowly, as well as less expansion of the upper layers of the ocean as they warm), the researchers note. But a reduction in the number and intensity of large hurricanes driving ocean waters on shore—such as this month’s Hurricane Joaquin, seen, which reached category 4 strength—may also play a role by cooling sea-surface temperatures that fuel the growth of these monster storms, the team notes. The strategy isn’t cheap: A 2009 study estimated that using aircraft to spray just 2 million metric tons of sulfur dioxide into the stratosphere would cost anywhere between $225 million and about $4.2 billion each year. And there could be unforeseen downsides, the researchers say, such as a decrease in stratospheric ozone or a shift in tropical weather patterns that could end up aggravating droughts in arid regions.
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