Perhaps we'll remember the week of July 21, 2019 as the first teaser trailer for the apocalypse. Or maybe we're farther along than that. After all, it was 108 degrees in Paris on Thursday—and not Paris, Texas, either. The Arctic is on fire. And the American West has a bit of a water problem, in that there isn't very much of it.
But it was America's most populous city that played host to a series of events this past week that may best encapsulate the range of horrors that await the human race now that we've proven ourselves determined to ignore the warnings of scientists. We've chosen instead to continue pulling coal and gas and oil out of the ground and to set fire to them at an alarming rate, a process which produces energy and lots of money for the people doing the burning. It also releases the gas, carbon dioxide, that is gathering in our atmosphere to heat up and destabilize our planet and threaten the future of human civilization as we know it. New York City just showed us what that might look like: more hot days, hotter hot days, and extreme rain events that will be more extreme. It wasn't never-before-seen, but the science indicates it will soon be the scene far more frequently.
On July 21, the temperature in New York hit 100 degrees. Historically, the city of New York has seen two days a year where the heat index—temperature plus humidity, or what it feels like outside—reaches 100 degrees or higher. But recent research suggests that extreme heat events will be more and more common in the coming years. By midcentury, if we take no action to mitigate the effects of climate change, it will be 18 days. (Chicago will go from three to 26. Dallas will go from 30 to 92. Even Green Bay will go from one to 10.) This past Sunday, it was hot enough in New York to drive electricity demand to the point that the city experienced partial blackouts in Brooklyn. ConEdison also reported equipment failures. That followed a blackout in Manhattan's Midtown and Upper West Side earlier in the month.
And that was just the fire. The next day, the city got the main event of our climate-crisis teaser: the water. A summer thunderstorm rolled into town—again, not unprecedented—but the results were fairly biblical. At one point, three inches of rain an hour were falling in Brooklyn, and it led to devastating scenes, particularly in the area around Carroll Street and Fourth Avenue, a topographical low point where the water ran down from neighboring Park Slope and gathered in massive volume. The videos from bystanders made the oft-and-understandably ridiculed Day After Tomorrow look a little less ridiculous.
At 4th Ave and Carroll Street in Brooklyn. Courtesy of Adrienne Zhao pic.twitter.com/wEU4RFwqfQ— Julie Chang (@BayAreaJulie) July 22, 2019
"The basic thing that makes extreme precipitation events heavier in the warmer climate is that there’s more water vapor in the air, and that’s a pretty unquestioned consequence of warming," says Adam Sobel, professor of applied physics and applied mathematics at Columbia University. "The amount of water vapor in the atmosphere increases roughly about seven percent per degree Celsius. And so, the baseline expectation is that heavy rain events get heavier at about that rate also. Some models increase them faster than that, and some slower." It's too soon to draw direct conclusions about whether climate change had an effect on Monday's storm specifically, but it very likely fits in this established pattern.
Total annual rainfall is only expected to increase two or three percent globally over the coming decades, but the real effects of warming will be felt in individual extreme events. There won't necessarily be more of them, but they will be more severe. 2017's Hurricane Harvey was a prime example of this: the storm reportedly dropped 27 trillion gallons of water on Texas and Louisiana, and hit the city of Houston particularly hard. It was also so destructive—the storm caused $125 billion in damage, behind only Hurricane Katrina all-time—because Harvey moved so slowly, and hovered over the Gulf Coast area for days. Sobel says there's some new research that the storm's glacial pace of movement may also have been tied to warming temperatures, but it lacks the widespread acceptance that the water vapor theories have. Of course, scientists are extremely confident that warmer ocean temperatures also lead to more ferocious storms, as wind speeds pick up and supercharge the cyclone's destructive potential.
One factor in Houston was the sheer amount of asphalt and cement that covers the city. These surfaces do not take on water in the way that earth does, and can lead to more severe flooding events. As storms begin to drop more water, faster thanks to warming temperatures, this effect will be magnified. New York has the same problem: as much as 70 percent of the city's surface is covered by minimally absorptive surfaces like these. This puts New York's 7,500 miles of sewer—which, if you laid it out, would stretch to California and back—under additional strain in "flash" events like the one this week.
"With further development in many parts of the city—and Brooklyn is one of them, of course—you have more paved surfaces, and so the water that comes down cannot penetrate as readily into the ground," says Klaus Jacob, a special research scientist at Columbia. "And so, you have increased runoff into the streets, and the sewer system is not able to absorb it all through the limited openings that are available. So, it accumulates on the streets and floods."
Some cities, including New York, are taking measures to mitigate the damage of the coming floods—a longstanding factor in coastal city life that will grow worse as heavy precipitation events get heavier. The city's Department of Environmental Protection is building out and renovating the sewer system, but the department sees a better bang-for-your-buck in taking measures above ground. Building sewer or digging it up is incredibly expensive, and you also run into the basic problem of how much stuff is already occupying space underground in one of America's oldest and largest metropolises. There are pipes, sure, but also power lines and subway corridors and alligators. There are already two massive sewer lines under that Carroll Street-Fourth Avenue area, for instance, but they were absolutely overcome by the storm this week. There was just too much water.
"What we've been trying to do is learn how you can flood by design, meaning that you create spaces that can fill up with water," says Alan Cohn, the managing director of Integrated Water Management at DEP. The department has embarked on a sprawling project building "rain gardens" throughout the city—specialized sidewalk cutouts designed to take on thousands of gallons of water, thereby reducing the strain on the sewer system. That's part of a wider "green infrastructure" initiative across the city.
The DEP is also exploring more cutting-edge flood-control techniques and taking cues from Copenhagen, which has jumped to lead the pack after a major cloud-burst event in 2011 where six inches of rain fell in two hours. It caused $1 billion in damage. Denmark's capital has undertaken a major initiative to revamp streets and parks to take on as much water as possible. They've even sought to use basketball courts as emergency reservoirs, storing water above or below the surface to prevent it running into the sewers all at once. New York has begun a pilot program in Queens—one of many historically underserved areas when it comes to drainage and sewage and sanitation systems—to introduce some of these ideas while simultaneously seeking some environmental justice.
New York is ahead of the curve when it comes to climate-change adaptation, along with San Francisco and cities beyond our borders like Toronto, Rotterdam, and London. In the end, though, there's only so much any city can do.
"There are limits to engineered solutions no matter what," Cohn, from the DEP, says. "There will always be a threshold beyond which it will flood. So it comes down to risk tolerance, and how much we can invest in these systems."
If we do not stop pumping carbon into the atmosphere at this rate, we're bound to have a lot more weeks like this—or worse. After all, the heat wave and the rain did not arrive together by accident.
"It's not a coincidence that you had a severe heat wave followed by heavy rain," Sobel says. The thunderstorm feeds off the energy of the heat system ahead of it, a relationship that's independent of global warming. It's called a "compound event," Sobel notes, and "given that they often are dynamically coupled in this way, it's plausible to expect this to be a more common occurrence."
This is the first summer of the rest of our lives. It is safe to expect more extreme heat events that put severe strain on the power grid and pose a threat to public health—particularly for children, the elderly, and the infirm. It's also safe to expect some of those heat waves to be closely followed by extreme precipitation events, where the sky opens up to drown our cities. We've already seen the great Midwestern floods of 2019, and towns that lack New York's size and resources will face these conditions, too. The heat will break, but only at the cost of a flood. And then we'll do the whole thing again, over and over, and ask ourselves how we did not stand on the rooftops and scream for a stop to all this before it spiraled beyond our control. How's the weather looking this weekend?
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