Every two to seven years, the equatorial Pacific Ocean gets up to 3°C warmer (what we know as an El Niño event) or colder (La Niña) than usual, triggering a cascade of effects felt around the world. This cycle is called the El Niño Southern Oscillation (ENSO) because every El Niño is naturally followed by a La Niña and vice versa, with some months of neutral conditions in between events. The change in sea surface temperature associated with ENSO events might seem marginal, but it is more than enough to disrupt weather patterns globally and even the large-scale circulation of air in the polar stratosphere 8km above the Earth.