Pay attention to what happened to Houston. It is rare to be given such a vivid look at our collective future.
Climate change cannot be definitively blamed for Hurricane Harvey, but it likely did make the storm more powerful. Global warming did not conjure the rains that flooded the nation's fourth-largest city, but it likely did make them more torrential. The spectacle of rescue boats plying the streets of a major metropolis is something we surely will see again. The question is how often.
The relationship between climate and weather is undeniable but never specific. Tropical cyclones do not batter Siberia's arctic coast and heavy snowfalls do not blanket the beaches of Barbados because the climates are different. But no one blizzard or hurricane can be attributed to climate change beyond the shadow of a doubt — which opens anyone who raises the subject at a time like this to the accusation of "politicizing" a disaster.
The science explaining climate change is clear, however, no matter what deniers such as President Trump choose to believe. And it will be political decisions that determine how often we witness scenes of devastation such as those in Houston.
Begin with the basic fact of a warming planet, due primarily to greenhouse gas emissions from the burning of fossil fuels. The waters of the Gulf of Mexico are unusually warm this summer — between two degrees and three degrees above normal — which gave Harvey extra energy and moisture.
Hurricanes usually weaken when they approach a coastline, but Harvey was able to gain strength, making landfall as a Category 4 storm. According to Penn State University professor Michael Mann, one of the world's leading experts on climate change, Harvey's unprecedented rainfall totals were likely boosted by global warming in at least two ways. Higher atmospheric and ocean temperatures mean more evaporation, he wrote in The Guardian, which means more precipitation. And the fact that the storm parked itself so stubbornly over Houston is due to a jet-stream pattern predicted in scientists' climate-change models.
Since 2005, we've had Katrina, Sandy and now Harvey. The flood next time could come in Corpus Christi, Mobile, Pensacola, Tampa Bay, Naples, Miami, Jacksonville, Savannah, Charleston — no one knows where. But there is no doubt that it will come.
Humankind has boosted the concentration of carbon dioxide in the atmosphere by a shocking 40 percent since the beginning of the Industrial Revolution, when we started burning fossil fuels on a large scale. Even if carbon emissions were magically ended tomorrow, warming would continue for many years. But we can — if we choose — keep climate change from getting catastrophically out of hand.
The rest of the industrialized world has decided to move toward a clean-energy future — and reap the economic benefits such a shift can entail. I'm betting that Trump's successor, whether a Democrat or a Republican, will reverse his shortsighted, self-defeating decision to withdraw from the Paris climate accord.
But in addition to mitigating climate change, we must adapt to the warming we have made inevitable. Houston officials at least tried to learn one lesson: In 2005, as Hurricane Rita approached, officials ordered an evacuation that turned freeways into parking lots; about 100 people died in the chaos. This time, residents were advised to stay put — and, from what we know so far, there appears to have been much less loss of life.
But billions of dollars' worth of private and public infrastructure is being destroyed. Since low-lying coastal cities are not likely to pick up and move inland, they are going to need new natural or artificial barriers to protect against storm surge (which might have been the big problem with Harvey, but wasn't) and high-capacity drainage systems to alleviate flooding (which was).
Such projects are hugely expensive — but cheaper than repairing the damage from a citywide flood.
Also, the nation needs a sustainable way of providing flood insurance to those living in vulnerable areas. The current National Flood Insurance Program charges rates that do not nearly cover its outlays, and for years it relied on out-of-date maps that did not accurately show flood risks.
Buildings, meanwhile, can be made more flood-proof. President Obama signed an executive order requiring builders who receive federal funds for a project to account for the risk of flooding in their construction plans. Trump rescinded the measure, saying it was "job-killing." How many people went to work in Houston today?
Folks, nature is telling us something. How many "100-year" storms or "1,000-year" floods will it take for us to listen?
Eugene Robinson is a columnist for the Washington Post.