Let’s get the obvious thing out of the way first, shall we? There may never have been a better week in the history of the modern world — or at least recent cinema — to release a movie with “Greenland” in the title.

Just in case you’re reading this from another era or galaxy, you’ll see what we mean if you Google “United States” and “Greenland.” Otherwise, not much more needs to be said.

Except that “Greenland 2: Migration,” a serviceable but rather low-key, even grim affair starring a sturdy, understandably melancholy Gerard Butler, would make anyone want to get the heck out of Greenland — not find a way to own it. That’s because the movie, Ric Roman Waugh’s sequel to his comet-disaster film of 2020, presents a Greenland that, like most of the world, has been reduced to an unlivable mess of radioactive ash, with life only possible in a dank underground bunker.

And that’s before things get even worse, forcing everyone to flee before a tidal wave flattens them. Hence the truly important word in the title: “Migration.”

Butler returns as John Garrity, and Morena Baccarin as his wife, Allison. At the screening I saw, Butler popped on-screen beforehand to welcome viewers and tell them the sequel is “just as intense, but with more emotion.” That seems to be the goal, and Baccarin’s main job: her Allison is the vehicle for fear, anxiety and sadness, while John is mostly the strong silent type, though with an affinity for poetry. A new addition is Roman Griffin Davis as their 15-year-old son Nathan, who’s growing up in less than ideal circumstances.

It’s been five years since the Clarke meteor struck Earth and destroyed two-thirds of it. Images from the first film return as a reminder — the Eiffel Tower clipped in half and bent like a mangled metal toy, the Sydney Opera House just recognizable amid the ash.

When we left the Garritys, they were among the planet’s lucky survivors, having made it to the Greenland bunker. Now, nobody feels too lucky, though there’s an effort to recapture some rhythms of normal life: school, evening socials with dancing, exercise class. The outside remains off limits to most. John, a surface scavenger, takes dangerous trips up in a gas mask. It’s a bleak existence, especially for a teenager like Nathan, who’s taken to briefly sneaking out.

A meeting of the bunker’s governing committee, on which Allison sits, shows how precarious things are getting. “We’re basically running on fumes,” someone says. Besides the toxic radiation, the comet is still sending forth destructive fragments. Can we go to Iceland, they wonder? No, that’s gone. Same with Canada. And most of Europe.

Except, maybe, southern France. One expert posits that the impact left a crater there, a safe zone with clean air where human life can not only survive, but thrive. And where the grass is, quite literally, greener.

Meanwhile, a bit of social conflict comes into play when one member suggests that a group of migrants seeking shelter be denied entry. Allison argues to save them, and wins.

It all becomes moot when a brutal earthquake destroys the bunker itself. The family races to the shore and manages to reach a small rescue craft with a few others before a tsunami hits.

The craft runs out of gas, but manages to land … in Liverpool, a partly submerged metropolis which resembles, say, Venice after a volcanic eruption. (These intermittent scenes of postapocalyptic cities and barren landscapes are what Waugh does best.)

There’s not exactly a warm welcome. But the family manages to find a car and pay its driver to take them toward London, where Allison has a dear friend. “The world is a dangerous place now,” the man says, unnecessarily.

Obviously, more harrowing journeys ensue. One will involve a death-defying trip across the English Channel — or what remains of it — some of it on bridges seemingly made of only rope.

The family meets various people along the way, none particularly memorable. This sequel may be focused more on emotion and character — since the whole comet thing happened long ago — but the problem is, none of this is compellingly rendered, and is forgotten when convenient. A relationship between young Nathan and a sweet girl he meets, for example, is basically dropped.

Will the family make it to France, and does the beautiful crater exist? That’s the part we can’t tell you. As for the “Greenland” of it all — well, Greenland is forgotten early, and even when we were there, it was nothing to write home about. But hey — it makes for a pretty fortunate title.

“Greenland 2: Migration,” a Lionsgate release, has been rated PG-13 by the Motion Picture Association “for some strong violence, bloody images, and action.” Running time: 98 minutes. One and a half stars out of four.