By Eric Klienberg for The New Yorker.

Hurricane Patricia, which hit southwestern Mexico last weekend, was the largest recorded hurricane to make landfall off the Pacific, but it was not the only historic storm this October. At the beginning of the month, a tropical weather system formed southwest of Bermuda and intensified into a Category 4 hurricane, with heavy rain and surface winds reaching a hundred and fifty-five miles per hour. Meteorologists called it Joaquin, and predicted that the dangerous storm would soon turn northeast. According to their models, New York City and the surrounding coastal region fell directly within the “cone of uncertainty” where Joaquin could make landfall. New York Governor Andrew Cuomo activated the State Emergency Operations Center, and New Jersey Governor Chris Christie declared a state of emergency, warning that major flooding events were likely. No one wanted to be caught unprepared. (Joaquin did turn out to be lethal and devastating–but in South Carolina, where it joined with other storms to cause severe flooding and fifteen deaths, and in the Bahamas, where it slammed several islands and sank a cargo ship, killing all thirty-three of its crewmembers.)

Planning cities for climate change requires going far beyond updated building codes; it also involves what Klaus Jacob calls “pro-building” structures and infrastructures in anticipation of a warmer, wetter, and wilder world.

One clear consequence of Superstorm Sandy, which struck the New York City area in 2012, is that everyone, even climate-change deniers, takes planning for extreme weather events more seriously. After Sandy, I reported on why the region’s vital systems for energy, transit, health care, and communications proved so vulnerable to the storm surge. Since then, federal and state governments have spent billions of dollars to rebuild critical infrastructure; hospitals and utilities providers have made major investments in climate security; and “resilience” has become a buzzword in philanthropic and policy circles. Neither adaptation nor resilience is a sufficient response to global warming. Mitigation, which requires converting to an energy system based on renewable resources like sun and wind, is far more urgent. But because the carbon dioxide that we’ve already emitted will produce many decades of rising sea levels, higher temperatures, and more dangerous weather, we have no choice but to adapt. This week, the third anniversary of Sandy, is a fine time to ask what changes the superstorm inspired, and what work remains.

During Sandy, corrosive stormwater quickly inundated the subterranean arteries that connect New York and New Jersey, generating widespread damage and causing years of episodic delays on Amtrak, New Jersey Transit, the Metropolitan Transportation Authority, and the Battery tunnels, as workers slowly repair what is, at best, a woefully inadequate transit system. In New York City, the M.T.A. received four billion dollars in federal money for Sandy recovery and resiliency work, which it has spent on innovative deployable flood barriers, such as the Flex Gate and the Resilient Tunnel Plug, more water-resistant submarine cable, two new pump trains, and structural improvements to the tunnels. But Klaus Jacob, the Columbia University geophysicist who issued prophetic warnings about the city’s fragile infrastructure before Sandy, worries about other openings, “like subway entrances and open-sidewalk ventilation grids.” As he sees it, despite the system upgrades, “most M.T.A. facilities and operations remain vulnerable.”