Atlantic and Pacific Oscillations Lost in the Noise

Typography

According to the researchers, if the Atlantic Multidecadal or Pacific Decadal oscillations existed, there would be evidence for their existence across the suite of current state-of-the-art climate model simulations.

The Atlantic Multidecadal Oscillation (AMO) and the Pacific Decadal Oscillation (PDO) do not appear to exist, according to a team of meteorologists who believe this has implications for both the validity of previous studies attributing past trends to these hypothetical natural oscillations and for the prospects of decade-scale climate predictability.

Using both observational data and climate model simulations, the researchers showed that there was no consistent evidence for decadal or longer-term internal oscillatory signals that could be differentiated from climatic noise — random year to year variation. The only verifiable oscillation is the well-known El Niño/Southern Oscillation (ENSO).

"A distinct — 40 to 50 year timescale — spectral peak that appears in global surface temperature observations appears to reflect the response of the climate system to a combination of anthropogenic and natural forcing rather than any intrinsic internal oscillation," the researchers report today (Jan. 3) in Nature Communications.

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