Once a year or so, journalists from major news outlets travel to the Marshall Islands, a remote chain of volcanic islands and coral atolls in the Pacific Ocean, to report in panicked tones that the island nation is vanishing because of climate change. Their dispatches are often filled with raw emotion and suggest that residents are fleeing atolls swiftly sinking into the sea.

Yet new research shows that this is not the entire—or even an accurate—picture. Acknowledging this doesn’t mean that global warming isn’t real, or that...