UNTIL America gets a grand military parade, a drive along the wharf at Naval Station Norfolk, in Virginia, is the next-best thing. Destroyers, missile-cruisers, nuclear-powered submarines and, most fearsome of all, two 333-metre (1,092-foot) Nimitz-class aircraft-carriers, are enough to make Americans’ spines tingle and enemies shudder. But the menace that most concerns Captain Dean VanderLey, the chief civil engineer for the navy in the mid-Atlantic region, is one that is undeterred by military might. In the 100 years since the base was first built, the sea level has risen by half a metre. In a major hurricane, he says, while surveying the piers and a road linking them to an airfield, “a lot of this would probably be flooded”.

Captain VanderLey is not alone in fretting about the military consequences of climate change. A report published on January 26th by the Department of Defence (DoD) found that more than half of the 3,500 sites surveyed are already reporting climate-related problems (see map). Droughts are leading to water shortages, heatwaves are causing some live-fire exercises to be cancelled and shifting wind patterns are disrupting aircraft sorties.

Then there is the flooding. On February 18th scientists involved in the federal government’s National Climate Assessment, a four-yearly exercise mandated by Congress, presented an update to the last report from November, showing that sea levels are rising twice as fast as 25 years ago. In 2009 the DoD found that 128 coastal installations, including 56 naval ones, would be at risk if sea levels rose by a metre. The Navy’s sites alone were valued at $100bn. In 2016 the Union of Concerned Scientists found that nine strategically important bases, including several in the Hampton Roads region around Norfolk, could permanently lose half their land area by 2100 if waters rise by two metres. Critical outposts abroad are similarly vulnerable. Twenty years from now a new $1bn radar installed on the Marshall Islands, which helps to shield America and its allies from nuclear-tipped missiles launched by North Korea, could be under water. Diego Garcia, a staging post on an Indian Ocean atoll crucial for operations in the Persian Gulf, may be submerged too. President Donald Trump’s policies, which include pulling America out of the Paris climate agreement to limit global warming and championing coal, make all this more likely. In the past two months his administration has put his climate-sceptical stamp on the national-security and defence strategies. These documents, which each administration must draw up, lay out a high-level plan for keeping America safe. Under Barack Obama, they listed climate change as a strategic threat to be assessed and countered. Yet in a contradiction that is typical of this White House, other parts of the government are carrying on with planning for a warmer planet regardless.

As global temperatures rise so does the likelihood of extreme weather, with calls for military assistance in disaster relief. Last September the USS Wasp helicopter-carrier was sailing from Norfolk to Japan when it was diverted to hurricane-struck US Virgin Islands, Dominica and Puerto Rico. Melting sea ice in the Arctic opens up a new theatre of operations, especially against a belligerent Russia. As it thaws, the Bering Strait could become another strategic choke-point like those of Hormuz (the gateway to the Gulf) or Malacca (which connects the Indian and Pacific Oceans). Some studies have linked global warming to unrest such as the Arab spring. James Mattis, the defence secretary, has called climate change “a driver of instability”.

In December, days before he unveiled his climate-changeless national-security strategy, Mr Trump signed a defence bill that called climate change “a direct threat” and required the DoD to report which assets are at risk. He kept his chief climate envoy, George Banks, on the National Security Council. (Unable to gain a security clearance, Mr Banks resigned in February.) The Pentagon betrays no intention of shredding Obama-era rules directing the armed services to assess and counter climate-related weaknesses. It helps that the military bureaucracy is more hulking Nimitz than nimble corvette, remarks Ann Phillips, a retired admiral formerly involved in the Navy’s climate-planning: “It takes time to turn around.”

Bureaucratic inertia is not the only reason why reality has changed less than the rhetoric would imply. As David Titley, another retired admiral now at Pennsylvania State University, observes, Mr Trump is the mirror-image of Mr Obama, who stressed the security implications of climate change but did little to tackle them. Even before Mr Trump took office a year ago, Captain VanderLey’s construction budgets never included extra dollars earmarked for climate adaptation (or “resilience” as he prefers to call it, studiously avoiding talk of climate change). In practical terms, Mr Obama’s climate cheerleading can sometimes be hard to tell apart from Trumpian neglect.

100,000 tonnes of floating diplomacy

Former officials insist that during the last six years of Mr Obama’s presidency, Republican majorities in Congress would simply have blocked measures overtly aimed at combating global warming. Some money was (and still is) buried in the DOD’s notoriously opaque budget, they say. The White House and Congress leave the men in uniform lots of room to interpret what counts as a “threat”, notes Francesco Femia of the Centre for Climate and Security, a think-tank. Often, climate adaptation is a side-benefit of work motivated by other considerations. Norfolk’s four double-decker piers erected since the mid-1990s for $60m apiece were chiefly designed to ease access to electricity, water and internet cables that could previously only be reached by boat, and to accommodate modern ships’ higher decks, explains Joe Bouchard, a former commander of the base. If they also guard against encroaching seas, all the better.

Climate change is one among many threats facing American strategists. Others are more pressing, from North Korean nukes and Chinese island-building to wars in Afghanistan and Syria. But its importance is poised to grow as the Earth warms, so Mr Trump’s nonchalance looks myopic. For all its ponderous officialdom, the Pentagon also has an especially clear chain of command. What the man at the top considers important—or unimportant—therefore matters a great deal. Mr Trump might not hobble the armed forces’ efforts to deal with the consequences of climate change. But a more farsighted commander-in-chief would be adding to their armour.