It's an appropriate time to talk about hurricanes, and why "the worst ever" might be the new normal.
At its heart, a hurricane is just a thunderstorm on ‘roids. Actually, many thunderstorms all stuck together, swollen, agro, sweaty, and ready to lash out. In order to be classified as a hurricane, the storm has to have winds that are blowing at least 74 miles per hour. Those who are familiar with the hurricane rodeo know, however, that the danger posed by hurricane-force winds is only half the battle—the flooding that goes with a hurricane is as dangerous, if not more so, than the winds. Look at pictures from Katrina and Harvey and you'll quickly understand why that's the case.
They’re calling Harvey a 500-year (or even a 1,000-year) event, a term that can be misleading because the 500-year thing refers to probability, not history; essentially, in any given year, there is a one-in-500 (or .2%) chance of a storm like Harvey showing up and KO’ing Houston. In 2016, there was a .2% chance of a Harvey-esque storm hitting Houston, and in 2015 there was a .2% chance for Houston, etc. That makes it sound like just plain ol’ shit luck that Houston got 50+ inches of rain.
It’s not just luck, though. Or, it's not entirely luck.
As many have already pointed out, this is the third “500-year” storm for Houston in the past three years, and yes, according to the laws of probability, it is possible to have three vanishingly rare events happen three times in a row. After all, if you roll a dice a thousand times, it’s technically possible you’ll roll a six every single one of those times, but it’s not probable.
Something is monkeying with the probability of major storm events, and that “something” is, at least in part, climate change.
Perhaps you thought that climate change was only about longer summers and melting ice caps. (Insert picture of sad drowning polar bear here.) Sadly, that is not the case. Climate change has its fingers in many pies, and as Chris Mooney pointed out in “Storm World” way back in the ancient time of MMVII, climate change doesn’t necessarily increase the number of storms, but it sure as heck increases their intensity.
- Warm water evaporates more easily. You can easily see that when we heat water to a boil: it produces steam. It’s also why I use a humidifier in the winter—because cold air doesn’t hold much water.
- Hurricanes are created and fueled by warm water. Think of the wind as an engine, warm water as gasoline, and the rotation of the earth as a starter. (The earth’s rotation is what gives hurricanes their characteristic swirly shape.)
- If my crappy analogy doesn’t make sense, this video does a good job of explaining how a hurricane comes together.
- If warm water is gasoline, really warm water is like jet fuel and it makes that engine go like stink.
- Storm surge, the water that gets pushed up into coastal areas by a storm, has been made worse by sea level rise. A hurricane is shaped a little bit like a propeller, and as it turns, it acts propeller-like by shoving water away from its center. Where does that water end up? On land. In your city.
- The sea level is rising because our earth is a warmer place. You know how when you microwave a marshmallow it grows into a monstrous, misshapen blob? That’s because you’re applying heat to it, which causes it to expand. When you apply heat to the ocean, it expands and takes up more room, causing sea levels to rise.
- Sea level rise also affects our wetlands and estuaries by changing the composition of each. Wetlands and estuaries are things we super-duper want to have because they’re giant sticky sponges that absorb and slow storm surge.
Of course, we’ll never be able to draw a straight line from “climate change” to “Harvey” and say with one hundred percent certainty, Aha! Without that, we wouldn’t have had this! It’s looking less probable, though, that our Harveys and Katrinas are anomalies. You can't engineer a great environment for something and expect it not to show up and take advantage.
To all Harvey's victims and survivors, you're in my thoughts. Here's hoping this is the last 500-year storm of this decade.