What role has climate change played in the intensity of superstorms Harvey and Irma? While climate scientists still have much to learn about these storms, they have concluded for years that tropical storms are getting stronger and warned of more intense hurricanes and superstorms on the horizon.
In sheer rainfall measurement, Harvey was the wettest storm in the continental United States on record. The hurricane dumped 51.88 inches in a National Weather Service rain gauge at Mont Belvieu, a town near Houston. Even before Harvey, nine of the top ten single-day precipitation events occurred since 1990, according to the National Oceanic and Atmospheric Administration (NOAA). Such ferocious rainstorms are linked to warming trends – the average global temperatures in 2016 were a record 1.78 degrees Fahrenheit warmer than the mid-20th century mean, according to NOAA and NASA.
We are now dealing with another catastrophic storm, Hurricane Irma, the strongest Atlantic basic hurricane ever recorded outside the Gulf of Mexico and the Caribbean. It spent three days as a Category 5, the longest Category 5 hurricane since satellite storm-tracking began. On September 6, it became the first Atlantic storm to maintain wind speeds of 185 miles per hour for more than 24 hours.
As the planet’s temperature rises, the oceans absorb the bulk of the heat increase. The warmer water evaporates more, which increases the amount of humidity. A recent study, led by Dr. Gonjgie Wang of the Institute of Meteorology and Oceanography in Nanjing, China, and published in the journal Climate Dynamics, confirmed that three different ocean basins experienced “a robust warming in the past three decades.” The warming trend means a greater chance of more intense storms with heavier rainfall.
In addition, the warming trend in the Arctic causes stalled weather patterns that strengthened Harvey and Superstorm Sandy, which caused more damage than expected in 2012, said Charles H. Greene, a professor of earth and atmospheric sciences at Cornell University.
“With sea ice loss and Arctic amplification of greenhouse warming, the jet stream slows down, meanders more, and frequently results in stalled weather systems,” Greene said. “Houston would have suffered much less damage if Hurricane Harvey had just crashed through the city and petered out in west Texas. But instead, the storm system … stalled in place and [dumped] record amounts of rainfall from the Gulf on the city.”
Another stalled weather system - a high-pressure block over the Labrador Sea - prevented Sandy from veering out into the North Atlantic as the overwhelming majority of late-season hurricanes do. “Instead, it made a historically unprecedented beeline for New York and New Jersey, and the rest is history,” Greene noted.
The physical, emotional, financial and health hazards caused by these storms are staggering. Our response should be a call to action to support those in need, and to build more climate resilient communities and rapidly wind down our use of fossil fuels.
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