In a first, researchers have used chemical fingerprints locked within coral skeletons to build a season-by-season record of El Niño episodes dating back 400 years — a feat many experts regarded as impossible.

That record, presented in a new study appearing in the scientific journal Nature Geoscience, reveals an “extraordinary change” in the behavior of El Niño, according to the researchers. That shift “has serious implications for societies and ecosystems around the world.”

To conduct