A warm ocean off the coast of Peru can make winter in Moscow unusually mild. Such invisible threads linking weather in distant corners of the planet are called teleconnections. They were once thought of as permanent wiring: the signal sources may pulse, but the wires themselves lie still. New work shows that greenhouse gases have already rewired this circuitry.

Scientists compared two thirty-year periods: 1960–1990 and 1990–2020. They took temperature maps for every point on the globe and looked at how strongly these maps correlate with five major climate modes, including El Niño, the Indian Ocean Dipole, and the Pacific Decadal Oscillation. It turned out that over thirty years, connections changed over a fifth of the planet's surface. For El Niño, significant shifts affected 20% of grid cells; for the Indian Ocean Dipole, 15%; and for global mean temperature, 28%.

To distinguish an anthropogenic shift from natural variability, scientists compared the observed change in connections with a thousand random changes derived from a control model run without human influence. The observed shift was larger than any of the thousand random ones. This means the probability of attributing it to natural fluctuations is less than one in a thousand. Before this work, it was unclear whether the teleconnections themselves change under greenhouse gas forcing or whether the observed shifts were random. Now it is clear: the global restructuring of teleconnections between 1960–1990 and 1990–2020 cannot be explained by natural variability. It is attributed to human influence.