There are questions that require answers,
1. The source of internal variability;
2. how that evolves over time; and
3. how that modulates the planetary energy budget?
” We are living in a world driven out of equilibrium. Energy is constantly delivered from the sun to the earth. Some of the energy is converted chemically, while most of it is radiated back into space, or drives complex dissipative structures, with our weather being the best known example. We also find regular structures on much smaller scales, like the ripples in the windblown sand, the intricate structure of animal coats, the beautiful pattern of mollusks or even in the propagation of electrical signals in the heart muscle. It is the goal of pattern formation to understand nonequilibrium systems in which the nonlinearities conspire to generate spatio-temporal structures or pattern. Many of these systems can be described by coupled nonlinear partial differential equations, and one could argue that it is the field of pattern formation is trying to find unifying concepts underlying these equations.” http://www.ds.mpg.de/LFPB/chaos
Patterns in the Earth system are perturbation – greenhouse gases, solar, orbital variability – induced regime shifts in quasi standing waves – ENSO, PDO, AMO, AMOC, PNA, IOD, etc. – in the infinitely coupled spatio-temporal chaotic flow field of our spinning nonequilibrium planet.
It evolves as perpetual change in regimes at decadal to millennial scales. At a decadal scale in the modern era?
https://theconversation.com/is-the-global-warming-hiatus-over-45995
The PDO is part of the Interdecadal Pacific Oscillation (IPO) that has implications for the global energy budget via Rayleigh-Bénard convection – as in the Max Planck Institute link above.
But evident in TOA energy flux. It results in changes in the outgoing energy flux of the planet and modulates long term heat accumulation in oceans dependent on long term changes to the mean Pacific state especially.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2018GL077904
https://aip.scitation.org/doi/10.1063/1.4973593
https://journals.ametsoc.org/doi/10.1175/JCLI-D-17-0208.1
etc. etc.
Kevin Tremberth asked if the hiatus is over.
The gyre hypothesis is that solar mediated polar surface pressure anomalies drive ocean circulation in all the oceans – and upwelling in the eastern Pacific. The hiatus is about to start – within a decade perhaps as the sun dims and climate shifts again. If it is not happening now.
