From the conclusion:
We have tried to avoid discussion of causation, which, due to its controversial nature could lead to dismissal of the empirical relationship, and we want open a broader scientific discussion of solar coupling to the Earth and its environment. Nevertheless, independent of the exact coupling mechanisms, the question must be asked, why has the pattern occurred and reoccurred regularly for the past five solar cycles, or 60 years? We have only a few months at most to wait to see if this Terminator‐ENSO relation continues at the onset of the coming solar cycle 25. Should this next terminator be associated with a swing to La Niña then we must seriously consider the capability of coupled global terrestrial modeling efforts to capture “step‐function” events, and assess how complex the Sun‐Earth connection is, with particular attention to the relationship between incoming cosmic rays and clouds and precipitation over our oceans.
Jaime Jessop pulled out some more detail from the study:
What’s interesting is that the authors identify the past several decades as a ‘default El Nino like state’ when cloud cover in the Western Pacific has been depleted, coincident with a weakened Pacific Walker circulation and strengthened Brewer-Dobson circulation. During this period, they argue that ENSO has been uniquely sensitive to variations in solar activity:
Thus, over the past several decades the cloud pattern in the western Pacific has adopted an almost El Niño‐like default state, consistent with an observed eastward shift in precipitation in the tropical Pacific and weakening of the Walker circulation over the last century (Deser et al., 2004; Vecchi & Soden, 2007a), and which has been tied, via simple thermodynamics, to a warmer atmosphere.
Thus, it is entirely plausible that since changes in the (upper) atmosphere brought on by a strengthened Brewer‐Dobson circulation, weakened Pacific Walker circulation, and less cloudy Western Pacific, enables the relatively constant terminator‐driven changes to have sufficient “impact” to flip the system from El Niño to La Niña, independent of the actual mechanism that couples solar changes to clouds and ENSO.
The 2020 termination of the last Hale cycle, marked by the end of SC24 and beginning of SC25 is, according to Valentina Zharkhova, the beginning of a Maunder-like Minimum which will last from 2020-2053. If, as she suggests, global surface temperatures decline during this period, then we might expect the relationship between Terminator events and the switch from El Nino to La Nina to become less pronounced. The current progression of the Pacific to a La Nina may in fact be the beginning of a phase change from an ‘El Nino-like default state’ to a La Nina-like default state where, ironically, solar activity has less of an influence on central Pacific ocean surface temperatures.
Solar activity [image credit: NASA]
What drives the weather can drive the climate. In this case the chances of non-correlation are said to be extremely low.
A new study shows a correlation between the end of solar cycles and a switch from El Nino to La Nina conditions in the Pacific Ocean, suggesting that solar variability can drive seasonal weather variability on Earth, Phys.org reports.
If the connection outlined in the journal Earth and Space Science holds up, it could significantly improve the predictability of the largest El Nino and La Nina events, which have a number of seasonal climate effects over land.
For example, the southern United States tends to be warmer and drier during a La Nina, while the northern U.S. tends to be colder and wetter.
“Energy from the Sun is the major driver of our entire Earth system and makes life on Earth possible,”…
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