It’s not easy figuring out how cities should adapt to future sea-level rise. At the rate we’re heating the planet, many scientists now expect the ice caps to melt enough to hike ocean levels three to four feet by 2100. But then you have to look at how those higher seas interact with potentially fiercer storm surges. And then you have to survey a bunch of cities and guess how fast they’ll expand in the coming decades, to get a sense for just how many people will be at risk.

Tedious work. Fortunately, a new OECD report, put together by a group of climate modelers and risk-management experts, crunches the numbers for us. The report tries to give a sense of which cities will be most vulnerable to coastal flooding in the 2070s — assuming global warming keeps chugging along at its current pace. Here’s a top 20 list:

Things don’t look good for India. But the United States doesn’t get off easy, either. If you look at exposed assets rather than total population, then Miami, New York-Newark, New Orleans and Virginia Beach all climb higher on the list, with $7 trillion in assets vulnerable to severe coastal flooding by 2070.

Now, the OECD report notes that global warming isn’t entirely to blame for the expected uptick in exposed population, though it plays a big role. A lot of cities are also putting themselves at greater risk because they’re growing rapidly and not taking enough measures to shore up their flood defenses. And it’s not just poorer cities like Dhaka and Ho Chi Minh City that are struggling to adapt. Many rich cities are doing a shoddy job as well.

Take Miami. A three-foot sea-level rise, experts have noted, would likely put all of Miami Beach underwater and turn downtown Miami into an island, channeled off from the rest of Florida. Yet the state isn’t doing all that much to prepare for this eventuality. Instead, it’s racing to subsidize new developments along the coasts, through state-run insurance and funding for coastal protection. By contrast, cities such as London and Amsterdam are taking more prudent steps to guard against future flooding — and, as the OECD report notes, are likely to cope with sea-level rise better.

That’s not an isolated case. In general, the United States has been slow in preparing for rising sea levels. In many cases, we’re actively making things worse, as Steve Nash laid out in this excellent article in the New Republic. This is one area in particular where climate-change denial can do a lot of damage — it’s awfully hard to prepare for a problem that no one can agree even exists.