terça-feira, 29 de setembro de 2015

Study warns: Climate change will leave New York City underwater

We are constantly reminded that climate change will alter life on Earth as we know it, but people seem to go about their daily lives as if nothing is wrong. According to a report from the Washington Post, a new study aims to change that by bringing things a little closer to home. In the report, climates scientists warn that New York City is at a severe risk of storm-surge flooding.
The risk is significantly higher than it was 1000 and even 100 years ago. The report states that the increased risk of flooding is not only due to sea level rise, but to the increased intensity of coastal storms that often hit the Big Apple.
The researchers explained that they were seeing more intense storms that had a much easier time thrusting ocean water towards the land, citing The Battery as one of the NYC neighborhoods that has taken the biggest pounding from the ocean.
The paper was published in The Proceedings of the National Academy of Sciences by Andra Reed from Penn State University in conjunction with a group of other researchers including Reed’s colleague Michael Mann, MIT hurricane expert Kerry Emanuel, and Princeton’s Ning Lin. Emmanuel and Lin released a separate study earlier this September outlining the risks faced by Tampa, FL from the same types of intensified coastal storms.
The Atlantic Ocean is known for keeping hurricane damage to the coasts at a minimum, at least as far as records dating back to 1851 say. In reality, this time frame is too short to say if the risks to New York City’s coastal areas have significantly increased since before records started being taken, but the trends affecting the city line up with other trends in coastal regions around the world.
The research team attempted to make the best possible estimate of what hurricane records may have looked like from the years 850 to 1800 in the Atlantic Ocean. They simulate huge numbers of “downscaled” Atlantic coast hurricanes over these years, and compared them to storm surge records that were taken from hurricanes from 1970 to today, the period scientists call the “anthropogenic era.”
The researchers discovered something important in their models. One of the biggest variables that didn’t remain static was the level of the ocean off of New York’s coast. Using geological records from over 1,000 years of past sea levels from nearby New Jersey’s shore on the Atlantic, the synthetic storm surges modeled were each based off of the sea level’s position when the storm occurred.
So what does all of this mean? Storms varied widely over the last 1000 years on the Atlantic coast. One of the key findings is that sea levels are significantly higher than they were in 850 A.D. The sea level’s ascent has accelerated sharply over the past 100 years, and consequently, the average storm surge for hurricanes during the anthropogenic era, since 1970, has risen by a factor of nearly 1.24 meters. According to the study, these results highlight the ever-growing risk faced by coastal communities across the U.S. on account of rising sea levels combined with increasingly intense storm surges.
One of the most poignant examples, still fresh in the memories of countless residents living in New York City and up and down the northern East Coast, is superstorm Sandy. Researchers estimate that a storm of that intensity is so rare that it should only occur once every 3,000 years. With the changes to sea level and the increasing intensity of coastal storms, however, storms of this magnitude are more likely to show up at least once every century.
Rising sea levels pose the greatest risk. When climate studies refer to the sea level rising by less than a meter in some places, it really doesn’t seem like that big of a problem. You’re not even going to notice a meter less beach on your next visit to the shore, right?
The real risk lies in the destructive power of water. Have you ever tried to lift a full 10-gallon bucket? If you have, you will recall that is extremely heavy. Now, imagine how many of those buckets you would have to dump into the ocean to make the entire sea rise by just one meter. That’s a lot of extra water.
The additional water, which is added through a combination of melting ice from the polar regions and a phenomenon called thermal expansion, wherein the water molecules are actually spread further apart due to increased heat, has great destructive power. Combine this with the powerful currents and winds produced by a hurricane, and you have a recipe for disaster.
With higher waves traveling further inland during these storms, the risk for property damage becomes much higher. We all watched in 2012 as entire blocks of New York City were up to the trashcans in floodwater, subways closed, and cars floated aimlessly towards the sea as the streets drained. Billions of dollars of damage were caused up and down the coast, and that risk is only poised to increase with future storms.
The researchers further coaxed out the real risk of storm surges from their models due to changing sea levels. They did not find an average difference in the height of storm surges between the pre-and-post-anthropogenic eras, but a “long-tail” phenomenon that showed severe surges becoming more common and worse than before. The paper wrote, “The storm surge heights in the tails of the anthropogenic distributions are significantly greater than the storm surge heights in the tails of the pre-anthropogenic storm surge distributions.”
The researchers warn that the risk posed by future hurricanes will likely mimic what we saw with Hurricane Sandy in 2012. Climate change, they contend, is not something that we should be waiting for – we should already be dealing with it now.

Source: BAWB News

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