Was Hurricane Harvey the result of climate change? The answer is complicated because weather is complicated, and probably the best science can say, really, is “in part.” But in some very important ways the question is ultimately semantic. As journalist Robinson Meyer, at The Atlantic, and climate scientist Michael Mann, on Facebook, have explained very clearly and very helpfully, global warming has meant more moisture in the air, which intensifies rainfall and flooding, and significant sea-level rise, which leads to bigger and more invasive storm surges — these elements, along with lesser anthropogenic factors, account for as much as 30 percent of the deluge, according to one scientist Meyer spoke with. A storm a third weaker would still be devastating for the Texas Gulf, of course, considering Harvey’s likely rainfall is already over 40 inches in some spots, with another 15 to 25 to come. As of last week, the position of the city of Houston was that just 12 inches within 24 hours would be cause for total evacuation. But the more important matter is not how much blame for Harvey we should parcel out to climate change; it is how often, in this new age of epic weather, storms like this one will hit. There are complicated variables there, too, of course. But the big-picture answer is clear: much more often than we are prepared for — psychologically, socially, politically.
On Sunday, as the first dramatic images of a flooded Houston were pouring in, President Trump called Harvey “a once-in-500-year flood.” The term is not all that precise, but it is at least a very simple benchmark to understand: a storm so severe there is only a 1-in-500 chance we’d encounter something of its scale in any given year, meaning we should expect that kind of devastation only once every five centuries. To dwell on that figure just for a moment, it would mean a storm that struck once during the entire history of the Roman empire, or once during the entire history of Europeans in America: 500 years ago there were no English settlements across the Atlantic, so we are talking about a storm that would hit just once as Europeans arrived; established colonies; fought a revolution, a civil war, and two world wars; established an empire of cotton on the backs of slaves, freed them and then brutalized them in other ways; industrialized and post-industrialized; triumphed in the cold war, ushered in the “end of history” and witnessed, just a decade later, its dramatic return. One storm in all that time.
When was the last time Houston was hit by a “500-year” flood? Harvey is the third such flood in the last three years. Another struck less than 20 years ago, in 2001, when Tropical Storm Allison killed 22, stranded 30,000 residents, and wreaked $9 billion in damage. The damage done by Harvey is still being tabulated, of course; present estimates run as high as $40 billion, suggesting it could become the third costliest hurricane in American history. Inflation and economic growth are a factor in those assessments (as is development on flood plains), but nine of the ten costliest such hurricanes have struck since just 2001. To take but one additional case study close at hand, it is now estimated that New York City will suffer “500-year” floods once every 25 years. And sea-level rise is more dramatic elsewhere, which means that storm surges will be distributed unequally, too; in some places storms on that scale will hit even more frequently. The result is a terrifying, radically accelerated experience of extreme weather — centuries worth of natural disaster compressed into just a decade or two. By way of analogy, it may be worth considering what kind of suffering would result if centuries of disease, or famine, or conflict were visited on the planet in just a decade or two. Of course, climate change threatens to accelerate each of those plagues, too.
Americans used to call floods like this biblical. We haven’t dropped the term just because our public discourse has grown more secular over the decades, but because we understand that the threat, for all its horrific scale, has also grown much more quotidian. In my recent cover story surveying worst-case scenarios for climate change, I sketched out seven areas where our future could well be much worse, thanks to warming, than most of the public understands: heat stress, agriculture, infectious disease, war, economic growth, air quality, and ocean health. I didn’t focus on sea-level rise, since most engaged Americans seem already informed about that threat — at least the threat posed by median projections to places like Miami Beach and Bangladesh. I also didn’t focus on extreme weather, which seems likely to become the next aspect of climate change to come clearly into view for the average American. That is because they will see it, unmistakably; as Al Gore puts it in An Inconvenient Sequel, “Every night on the evening news is like a nature hike through the Book of Revelation.”
The superstorms have already begun to arrive more often, and even as we settle into thinking of natural disasters as a regular feature of our weather, the scope of devastation and horror they bring will not diminish, of course. The very partial news feed from Harvey has already showed this: a pastor looking for stranded motorists to fish out of flooded cars, city residents fishing fish out of floodwaters inside their homes, the city warning people not to take refuge in their attics unless armed with an ax to break through the roof when necessary. Ahead of the storm, the state of Texas cut off Houston’s air-quality monitors, fearing they’d be damaged; on Monday, a cloud of “unbearable” smells began drifting out of the city’s petrochemical plants.
The storm isn’t yet over, which means there is much more adversity and suffering to come — not just in Houston but as far along the coast as New Orleans, where the city is without a full complement of drain pumps after an August 5 storm. We are probably weeks, at least, from seeing the full scope of Harvey’s destruction, and further still from understanding just what kind of a rebuild is possible, and what kind necessary. But, on that question, that phrase “500-year” flood is very helpful to give context. Even a devastated community, buckled in suffering, can endure a long period of recovery if it is wealthy and politically stable and if it needs to do that only once a century. Perhaps even once every 50 years. But rebuilding for a decade in the wake of storms that hit once a decade, or once every two decades, is an entirely different matter, even for countries as rich as the United States and regions as well-off as greater Houston. For the world’s poor, it is almost impossible. And just now, according to the Red Cross, exceptional monsoon flooding has hit 7.1 million people in Bangladesh, 1.5 million in Nepal, and nearly 14 million India.
Rebuilding is not just a matter of wealth, of course. Politics matters, too. And here recent history counsels almost paralyzing despair. Put aside decades of Republican Party climate denial, which amounts to a “nothing to be done” abdication of responsibility to mitigate or prevent climate change on behalf of vulnerable citizens; and put aside the Trump administration’s efforts to undermine the climate legacy of the last president — efforts seemingly motivated so primarily out of spite that even their putative constituency, the oil and gas industries, think the policy rollbacks may be a bit too much and a bit too fast. Even ignoring all that, just this month President Trump’s FEMA boss Brock Long suggested the agency would cut back on support for flood insurance and disaster relief; and President Trump himself signed an executive order to eliminate Obama-era regulations that required new infrastructure to take account of sea-level rise. It had taken ten years of negotiating in the aftermath of Hurricane Katrina to get those regulations on the books; a decade after that storm, the city still hadn’t finished rebuilding its destroyed homes.
When Katrina hit New Orleans, it was not walloping a thriving city — the 2000 population of 480,000 had declined from a peak of over 600,000 in 1960. After the storm, it was as low as 230,000. Houston is a different case: One of the fastest-growing cities in the country — greater Houston even includes the fastest-growing suburb in the country — it has almost five times as many residents. It’s a tragic irony that many of those new arrivals who moved into the path of this storm over the last decades were brought there by the oil business, which has worked tirelessly to undermine public understanding of climate change and derail global attempts at reducing carbon emissions. One suspects this is not the last 500-year storm those workers will see before retirement. Nor the last to be seen by the hundreds of oil rigs off the coast of Houston, or the several thousand more bobbing now elsewhere off the Gulf Coast, before the toll of our emissions become so brutally clear that those rigs are finally retired, too.
*This post has been updated since its initial publication.