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.”


Cold, Hard Facts

Coldness can manifest where you least expect it: on a planet rapidly warmed by the combustion of fossil fuel, or in the heart of a star 250 times as massive as our own. On Greg Laden’s Blog, Greg explains that an apparent “recovery” of Arctic sea ice from its historic low in 2012 does not invalidate the long-term trend. Greg also explains this year’s legacy of extreme weather, such as snow in Cairo, writing that when there is less difference in temperature between equatorial and polar regions, “the jet streams get all wiggly and cause northerly air to reach far to the south in some places and southerly air to reach farther north in other places.” Meanwhile, on Starts With a Bang, Ethan Siegel explores the different fates awaiting stars of different sizes. When a star like our own runs out of fuel and begins to collapse, it blows off its outer layers and leaves behind a neutron star or small black hole. Bigger stars, however, start producing antimatter, which lowers the pressure in the star and generates gamma rays that heat up the core even further. These stars end in a pair-instability supernova, which “not only destroys the outer layers of the star, but the core as well, leaving absolutely nothing behind!” But in the biggest stars in the universe, gamma rays cause photodisintegration, which cools down the interior of the star and allows all its mass to collapse into a black hole. The earliest of these massive black holes probably seeded the centers of galaxies, which now contain millions of solar masses.