Harvey Floods Houston, Irma Makes History

Hurricane Harvey visited a near-biblical deluge upon Houston, dropping over 40 inches of rain on parts of the city. The situation resulted from warmer ocean waters, more moisture in the atmosphere, and Houston’s geography along with its preparedness for the disaster. Greg Laden shows hotter sea surface temperatures in the Tropics and the Gulf of Mexico allowed Harvey to gain extra strength as it formed and re-formed on its way to the United States. In another post, Greg asks if Houston’s infrastructure could have been better-prepared for this type of rainfall, suggesting that “Houston is proud of its Libertarian zoning laws” even though, as Ethan Siegel writes on Starts With a Bang, a stalled hurricane pouring down water “should be exactly what you’d expect for a city located where Houston is.”

On the other hand, while the city was swamped to the tune of perhaps $50 billion in property damage, very few people died from the catastrophe. William M. Connolley points out that global warming “made the storm stronger and pushed the rainfall up to ‘unprecedented’; but the CO2 used to make the infrastructure makes the deaths fewer.” Dozens of people are confirmed dead by Harvey’s hand, but a similar cyclone killed over 200 people in Sri Lanka and India in May.

On the heels of Harvey, Hurricane Irma swept up the Caribbean islands and on to Florida, causing more tens of billions of dollars in damage but failing to precipitate the doomsday scenario that many in the media foresaw. On Stoat, William M. Connolley asks if there’s any way to prove a relationship between global warming and these hurricanes, and offers up a wager for 2018. Meanwhile, Ethan Siegel notes that Harvey and Irma mark an historical milestone, as “two Category 4 (or stronger) hurricanes made landfall in the USA in the same year for the first time.” Ethan’s stance is unequivocal: “This is not simply a bad year or an unlucky coincidence, but is an effect of a planet that has been artificially warmed by human activity.”

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Haiyan and a Superstormy Future

Typhoon Haiyan, which made landfall in the Philippines on Nov. 7, is another sobering reminder of the severe weather we are provoking through climate change. It is unofficially the strongest recorded cyclone to ever make landfall, with wind speeds up to 195 mph, 70% stronger than Hurricane Sandy. Villages are flattened, and more than 5,000 people are confirmed dead (as of 11/22). Greg Laden says that tropical cyclones feed on heat energy from the sea’s surface, from seas we know are getting warmer. Haiyan was a storm that blew past the most dire classification, Category 5, which tops out at a sustained wind speed of about 155 mph. But Greg says the Saffir-Simpson scale is not really about wind speed, it’s about destructiveness, and sustained 155 mph winds are all you need for total destruction. So would it be a good idea to extend the scale to Category 6 or 7 for storms like Haiyan, or will this lead the public to feel that a Category 5 storm is less of a threat? Greg says we should focus less on the numbers and more on educating people on the dangers of cyclones, whose destructiveness will vary not only with wind speed but also with regional topology, the quality of infrastructure, and other local variables. Coby Beck on A Few Things Ill-Considered says “In addition to destructive winds, hurricanes bring storm surges and tremendous rainfall, both of which can pack a worse destructive punch than the direct effects of wind.” Coby suggests modifying the Saffir-Simpson scale with categories like 5B and 5C, which would reflect the increasing strength of storms like Haiyan without “diluting the ‘run for your life’ message category 5 is supposed to deliver.”

Posted to the homepage on November 11, 2013.