A large interstellar comet fragment striking Earth is a genuine astronomical possibility, and the resulting impact winter is scientifically grounded, so the underlying catastrophe is not fantasy. However, this sequel focuses on the aftermath years, and the specific chain of events depicted, a family trekking across a uniformly frozen Europe toward a habitable new home, compresses and dramatizes conditions in ways that lower overall plausibility. The odds of any single family experiencing this exact scenario are low, but the category of threat, a near extinction level cosmic impact, has real precedent in Earth's geological record.
The film keeps the human element believable, showing exhaustion, cold injury, difficult moral choices, and the desperation of survivors competing for shelter and supplies, which is where the Greenland franchise tends to be stronger than typical disaster fare. Family dynamics under stress feel earned. Where realism slips is in the physics of long distance foot travel through a frozen continent with limited food, fuel, and no medical support, which would in reality be far more lethal and slow than a 98 minute action adventure can portray. Some set pieces prioritize spectacle over consequence, but characters largely react the way frightened, protective people would.
