Zharkova’s model is supported not only by sunspot numbers and solar activity, but by other solar-studies fields: magnetohydrodynamics and helioseismology. In fact, the resulting data plots from these fields are so close to Zharkova’s model predictions, that the model could as well be based on either of those. So this model is not functioning in isolation from related science, but is in fact harmonizing quite well with it.
The Dalton extended minimum (1790-1830) is evidently an example of a Gleissberg minimum, while the deep and protracted Maunder minimum (1645-1715) was the previous ‘Grand’ minimum. It has been roughly 350 years since the onset of the Maunder minimum, and a bit over 200 years since the Dalton minimum began. Zharkova et al. also noted a moderate Gleissberg minimum in the earliest part of the 20th century, as well, so the periodicity for that cycle seems to be holding.
The gist of the matter is that all three main cycles are entering minimum phase, beginning with the end of this current solar cycle (Cycle 24). Cycle 25 will be even lower than 24, with 26 being very nearly flat-lined. Cycle 27 will begin to show a few signs of life, then there will be a gradual rise to full activity over several more solar cycles, even as the last three cycles have slowly decreased in levels. This means that the bottom of the extended, or ‘Grand’ minimum (to use Zharkova’s terminology), should run from ~2020 to ~2053. (NO, it will NOT last 400 years like some are reporting – that is the overall length of the Grand cycle, not the predicted length of the minimum.)
In terms of atmospheric interaction, certainly the majority of the solar radiation peaks in the visible range, and that changes little, and the atmosphere is largely transparent to it. Once it strikes a solid object, however, the photon’s energy is absorbed, and later re-radiated as infrared (IR), which the atmosphere largely blocks (at least in certain frequency windows), so it does not all radiate off into space at night. This is why things like rocks and masonry tend to feel warmer at night, and what helps drive the trade winds along shorelines – the temperature differential arising from the differing light absorption/IR re-radiation of water versus land.
But it turns out that, unlike visible light, higher-energy photons have a fairly strong correlation with the solar cycle; this includes ultraviolet (UV) and X-ray, most notably extreme UV or EUV, which borders the X-ray regime. Much of this photonic radiation is generated in the inner solar corona, because the corona’s activity strongly follows overall solar activity; much of the rest is produced during solar flares – which are PART OF solar activity. More, unlike visible light, this frequency regime is ENTIRELY absorbed in the upper atmosphere (exosphere, thermosphere, ionosphere). So during high solar activity, the EUV and X-ray radiation hitting Earth has 100% of its energy injected into the atmosphere. During low solar activity, there is considerably less energy from this high-frequency regime being injected into the atmosphere – according to NASA research I dug up in the course of researching her papers and presentation, it may completely bottom out – as in, essentially zero energy from EUV etc.
But that isn’t the only way this might affect Earth’s atmosphere. It turns out that the solar wind/corona effects shield the inner solar system from cosmic rays, which are very high energy particles coming in from cosmological sources, such as supernovae, quasars, pulsars, etc. As solar activity diminishes, the solar wind decreases in effect, and the cosmic ray flux (‘flux’ is a measure of number of units per square area, e.g. number of cosmic ray particles per square meter) increases. BUT we know that cosmic rays tend to hit atmosphere and ‘cascade’ – generate a shower of particles, rather like a branching domino effect – and this, in turn, tends to create condensation nuclei around which clouds can form. (In fact, our first cosmic ray detectors were so-called ‘cloud chambers’ where the formation of condensation clouds depicts the track of the particle.) As a result, increasing cosmic ray fluxes are apt to generate increased cloud cover; increased cloud cover will then block visible light from reaching Earth’s surface and adding energy to the overall system. And cosmic ray flux can vary by as much as 50% with solar variation.
Well, then. So. What effects are being seen as a result of these two items?