In the mid-1970s, a climate shift cooled sea surface temperatures in the central Pacific Ocean and warmed the coast of western North America, bringing long-range changes to the northern hemisphere.
After this climate shift waned, an era of frequent El Ninos and rising global temperatures began…
By studying the last 100 years of these cycles’ patterns, [the authors] find that the systems synchronized several times.
Further, in cases where the synchronous state was followed by an increase in the coupling strength among the cycles, the synchronous state was destroyed. Then. a new climate state emerged, associated with global temperature changes and El Nino/Southern Oscillation variability.
The authors show that this mechanism explains all global temperature tendency changes and El Nino variability in the 20th century.
I haven’t obtained the paper myself yet, but it certainly sounds interesting. Time will tell if their claim stands up to scrutiny, but it sounds like they have uncovered a plausible mechanism for explaining temperature changes that does not rely on greenhouse gas forcing.