The orchestra has been playing in the Pacific Ocean for over a century. Some instruments carry a fast melody, others draw out a slow bass line, and together they create a pattern of warm and cold patches on the water. Previously, climatologists could only hear the overall chord, but the new method of extreme-point symmetric decomposition (ESMD) works like a sound engineer: it splits the concert recording into separate tracks.

For each ocean point, the method isolated oscillations with different periods. For El Niño, the main parts are played by two waves: one lasting about 2.6 years, the other 5.5 years. The Pacific Decadal Oscillation (PDO) has its own lineup: 5.1 years, 11 years, and 22 years. The common five-year wave is that very instrument that makes the two phenomena sound alike.

The method can be applied to any climate data, from temperature to precipitation. This will help prepare in advance for droughts, floods, and changes in fisheries. At last, the orchestra can be heard instrument by instrument.