For thirty years, climatologists have been piecing together a shattered vase. Each climate model is its own shard, and they all promise different amounts of warming by 2100, from one and a half degrees to nearly six. The spread doesn't shrink no matter how much the models are improved. Inside this vase lives the ocean, which oscillates on its own with periods of 7 and 14 years, like a pendulum that no one pushes but that never stops. And the equations describing climate are such that the slightest change in how clouds or turbulence are described can flip the behavior of the entire system. The vase's shards keep splintering.
Scientists have changed tactics. Instead of precise gluing, they decided to add a glue that fills every gap. That glue is noise: random perturbations always present in the ocean due to turbulence.
Two models that without noise behaved differently become indistinguishable under its influence. It's like two people who seem different in a quiet room but behave the same in a noisy crowd. Perhaps noise is what will help assemble the climate vase into a whole, albeit with rough seams.
The Arnold circle map family describes the competition between two periodicities, such as the internal rhythm of El Niño and the annual cycle. In El Niño models, steps of the devil's staircase are indeed observed, corresponding to periods of 4 years, 2 years, and 16 months.