Not that long ago, the concept of sea level rise was just that — a concept. It was scary, but somewhat theoretical, or at least so far removed that someone else could deal with it. Someone far in the future, with better tools than us.

Wake up and smell the coffee, world.

A report issued this week by the National Oceanic and Atmospheric Administration estimates that sea levels surrounding the U.S. will rise by 10 to 12 inches on average by 2050 — basically surpassing the increases of the last 100 years in just three decades. “There will be water in the streets unless action is taken in more and more communities,” a NOAA oceanographer told The Washington Post upon the report’s release.

By 2050. That’s well within the lives of many of us. It means more frequent and far more destructive flooding and storm damage in coastal areas now home to 40% of the U.S. population and critical to the nation’s economy.

Moderate flooding that might now strike a vulnerable area every two to five years is likely to occur more than 10 times as often, several times a year in some places, NOAA suggests, and floods could come in clusters, saturating an area for weeks.

Of course, we knew this was coming. The last few years have brought atypical storms — to the East and Gulf coasts, especially — and in the aftermath we’re always warned that the effects of climate change mean this is getting nothing but worse. The year 2050 is just one benchmark; sea level rise will accelerate in the decades after that.

We’ve been told, and now we’re being told again. We really should be listening.

In Hawaii the effects will be somewhat less, 6 to 8 inches of sea level rise by 2050, but that’s still an amount that would be highly destructive given how much development is clustered right on the shore — all of Waikiki, to begin with.

Phil Thompson, director of the University of Hawaii’s Sea Level Center, told the Associated Press that conditions in Hawaii also are exacerbated by natural ocean conditions such as wave action and winter storms. If you need a visual: We’ve all seen the pictures of cars slogging through flooded streets in Mapunapuna — Thompson estimates that could occur 50 or 60 times a year, instead of just a few days now and then.

Beyond the property damage that flooding brings, myriad critical resources could be inundated by seawater, from storm drains to wastewater treatment to the aquifers that provide our drinking water to farmland, where increased salinity could threaten crops.

This is not meant to be a litany of hopeless scenarios, although we should all be quite thoroughly frightened.

NOAA’s report updates federal projections from 2017, the intent being to better inform government agencies, from the federal to the town levels, so they can protect their communities. It should be required reading for all Hawaii’s stakeholders.

And if a refresher course is needed, the “Hawai‘i Sea Level Rise Vulnerability and Adaptation Report,” issued by the Hawai‘i Climate Commission in 2017, laid out a raft of mitigations, including designating a statewide “vulnerability zone,” with land-use policies to protect critical cultural and economic interests while encouraging “managed retreat,” or the moving of structures inland where possible.

Future development should be encouraged outside the zone, the commission said, although the advancing sea would threaten so much acreage on Oahu that such development would have to be carefully balanced against agricultural and conservation needs inland.

All actions don’t have to be reactions, though. Global warming is the culprit here, and slowing its advance would slow the march of the sea. This means reducing greenhouse gas emissions, the overriding necessity as we confront our fears.