- Bom dia amigas e amigos deste oceânico blog.
- Selecionei a matéria baixo, publicada hoje no jornal THE WEEK, que explica minuciosamente porque os furacões vem se tornando mais frequentes e devastadores, a ponto de
serem chamados de furacões-mamute.
- Mamutes, creio que vocês todos sabem, que foram mamíferos ainda mais gigantescos que os elefantes.
Fernando Costa
How climate change causes extreme weather
September 24, 2018
Mammoth hurricanes have become more destructive and more common. Does climate change play a role? Here's everything you need to know:
Are hurricanes worsening?
Last year brought a trio of devastating Category 4 and 5 hurricanes: Harvey dumped a record-breaking 27 trillion gallons of rain on Texas; Irma was the most intense storm to hit the continental U.S. since Katrina; and Maria's winds reached 175 mph, flattening much of the Caribbean and knocking out Puerto Rico's entire power grid. Those storms killed thousands and did hundreds of billions of dollars in damage. They were very unusual in how quickly they intensified, how slowly they moved after making landfall, and how much rainfall they produced. Continuing that trend, Hurricane Florence exploded from Category 1 to 4 in barely 24 hours, traveling an astonishing 350-plus miles each day before slowing to an ominous crawl as it neared the Carolinas. The intensity of storms is growing so markedly that meteorologists have considered adding a Category 6 label in anticipation of future epic storms.
Is that because of global warming?
Scientists have debated the connection for years, but new research has provided strong evidence for that conclusion. Because Harvey crossed the Gulf of Mexico when waters were abnormally calm, scientists could collect highly specific data about ocean conditions before and after the storm. They found that energy leaving the ocean in the form of water vapor equaled the amount of energy dropped in rain — the first time that's been documented. There are two simple reasons why warmth exacerbates hurricanes. First, for every 1.8-degree Fahrenheit increase in temperature, the atmosphere can hold up to 10 percent more water. Second, a warmer ocean gives off more vapor, and the Gulf of Mexico was several degrees hotter than usual, leading scientists to estimate Harvey's rainfall was up to 38 percent greater than it would have been otherwise.
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How else are storms changing?
In June, Nature published the first study to analyze hurricane speeds worldwide. It found that hurricanes move about 10 percent more slowly over land than they did 50 years ago. The study's author, James Kossin, a scientist at the U.S. National Oceanic and Atmospheric Administration (NOAA), believes slower-moving hurricanes result from changes in wind currents caused by global warming. Naturally, more time lingering over land means more damage, and Kossin says a 10 percent reduction in hurricane speed corresponds with a 10 percent increase in rainfall. Warming also affects ocean currents, which could begin producing storms farther from the equator; as a result, hurricane season, now June 1 through November, could expand from late spring to winter. Warmer waters, however, can cause an "intensity-frequency trade-off," in which there are more severe storms but fewer weak ones... LINK
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