The ocean is not a calm bathtub but a living patchwork of warm and cold water. These patches are constantly moving, and their pattern is sometimes simple, sometimes tangled. Scientists have discovered that the degree of tangle in this pattern can predict El Niño, the warm current that arrives every few years and changes weather worldwide.
Previously, forecasts lost accuracy in spring, making it nearly impossible to predict El Niño's strength a year ahead. The new method looks not at the temperature itself but at its disorder: the more chaotic the temperature patches behave in one year, the stronger El Niño will be the next. For one dataset, the match is almost perfect: 99 out of 100.
It is like listening to the noise of a crowd: by the volume and disorder of the murmur, you can guess that something is about to happen, even without making out individual words. Now we have such a listener for the ocean.
For the 1997 event, one of the strongest of the century, the previous year's entropy was the highest in the entire observational record. The SysSampEn value for 1996 was 1.25, nearly twice that of years without El Niño.
In Kim Stanley Robinson's novel 'Forty Signs of Rain', scientists attempt to predict abrupt climate changes using nonlinear data analysis methods. SysSampEn is a real step in this direction: a complexity measure that reveals signals where classical models are blind.