Peter Huybers

In the mountains, an echo repeats any shout, and you can't immediately tell who shouted: a person or the wind. That's roughly how climate scientists work when they try to understand why an unusual heat wave or drought happened. They look for a human fingerprint in a weather disaster, but nature has its own voices that can sound similar.

A warm ocean off the coast of Peru can make winter in Moscow unusually mild. Climate scientists call these invisible threads that link weather in distant corners of the planet teleconnections. For a long time, they were thought of as something like permanent wiring: the signal sources may pulse, but the wires themselves lie still.