Evidence shows that the sky is coming down on our heads—the watery part of it, anyway, in larger and larger cascades. It’s largely our own fault.
The past two months have seen some doozies just in the U.S. The Empire State Building was struck by lightning twice on Monday during a storm that brought an inch of rain down in what felt like a single sheet.
Last month, at least 23 people died in West Virginia flooding. At its peak on June 23, more than 8 inches to 10 inches fell within half a day—a once-every-1,000 years rain storm. Maelstroms in May and early June dropped five times as much rain as normal near Houston, seriously challenging the definition of normal. More than a dozen people died. It was the city's fifth major flood in just over a year. (Rainfall is trending higher nationally, though paving over much of Texas probably doesn't help.)
The phenomenon is known in meteorology circles as the more sober “wet microburst.” They are supposed to happen rarely; conditions must be just right. A thunderstorm runs into a dry patch of air that sucks some moisture away. The air underneath the storm cloud cools, making it more dense than the air around it. The cooler air begins to drop into even warmer air and then accelerates. When the faucet really flips on, air can blast out of the sky at more than 115 miles per hour. It deflects off the ground and pushes winds outward, at or near tornado strength. The Phoenix event above was actually a “macroburst,” with a radar footprint wider than about 2.5 miles, said Amber Sullins, chief meteorologist at ABC-15 News.
Scientists understand the mechanics of small-scale weather events such as rain bombs, tornadoes, and severe thunderstorms. The past few years have seen modest improvements in projections of how these storms might behave in a changing atmosphere, region-by-region.
What’s known with much greater confidence by climatologists is that storms should continue to intensify. There's little question that by stockpiling water vapor, the atmosphere is building a worldwide arsenal of “rain bombs”—or, if you like, wet microbursts, macrobursts, or just your typical, Noah-scale deluges. And unlike, say, the study of climate change and its relationship to war, why the sky keeps falling is clearer:
- Human activity has increased the amount of carbon dioxide in the air by more than 40 percent above pre-industrial levels.
- The CO2 and other climate pollutants trap more heat in the atmosphere.
- A hotter atmosphere holds more water—about 4 percent more for every degree-Fahrenheit rise in average temperature.
- More water vapor and energy in the system mean more intense storms. And lots, and lots, and lots of water.
Scientists can’t say where the next rain bomb may land. They still don't know where lightning will strike next. But it’s clear from wide-ranging research that human activity has weaponized the atmosphere.