The Pacific Ocean is like a big pot of water. Sometimes warm water gathers near the coasts of South America, and that's called El Niño. Previously, it was thought that El Niño comes in only two flavors: a strong one near the coast and a weak one in the middle of the ocean. But new research shows that El Niño actually wears five masks, that is, five distinct types.

Scientists took ocean temperature data spanning 122 years and applied a clever method that doesn't force each event to be just one type. For instance, the 2015 El Niño is 80% extreme, 15% strong, and 5% weak. It's like looking at someone wearing a half-mask: you can't say exactly who they are, but you can estimate the odds. It turns out that since 1970, extreme El Niño and strong La Niña (the opposite phenomenon, when waters are cooler than usual) have become more frequent. As a result, the climate has become more jumpy.

Now that we know all five masks, we can test how well models predict the weather. If a model misses the extreme type, it makes mistakes. And that matters for everyone living in regions affected by El Niño: it brings drought to Australia, rain to Peru, and warm winters to Siberia.