The "Sun-climate" relationship : III. The solar flares, north-south sunspot arrea asymmetry and climate

In this last Paper III additional evidences that the solar high energetic particles radiation with energies higher as 100 MeV (the solar cosmic rays SCR) is an very important component for the “Sun- climate” relationship are given (see also Paper I and II). The total solar irradiance (TSI) and the galactic cosmic rays (GCR) variations given an integral climate effect of cooling in sunspot minima and warming in the sunspot maxima. Unlike the both ones the powerful solar corpuscular events plays a cooling climate role during the epochs of their heigh levels. By this one subcenturial global and regional temperature quasi- cyclic changes by duration of approximately 60 years could be track during the last 150 years of instrumental climate observations . It has been also evided in the paper that this subcenturial oscilation is very important in the Group sunspot number (GSN) data series since the Maunder minimum up to the end of 20th century. Thus the solar erruptive activity effect make the total “Sun -climate” relationship essentially more complicated as it could be follow when only the TSI and GCR variations are taken into account. In this light the climate warming tendency after AD 1975 is rather by a natural as by an antropogenic origin. Most probably the last one is very close related to the general downward tendency of erruptive solar events which is superimposed over the high long term TSI levels during the last three decades (AD 1975-2007). It is evided, that the efficiency of the solar corpuscular activuty over the climate is strongly depended by the “north-south” asymmetry of the solar activity centers (as a proxy the sunspots area north-south asymmetry index A is used there). The climate cooling effect in the Northern hemisphere is most powerful during the epochs of positive values of A.

💡 Research Summary

The paper attempts to broaden the conventional “Sun‑climate” paradigm, which typically focuses on variations in total solar irradiance (TSI) and galactic cosmic rays (GCR), by adding a third component: high‑energy solar cosmic rays (SCR) with energies above 100 MeV, produced mainly during solar flares and coronal mass ejections (CMEs). The author argues that while TSI and GCR together generate a classic pattern of cooling during sunspot minima and warming during sunspot maxima, the episodic bursts of energetic particles associated with strong eruptive solar events exert a net cooling influence on Earth’s climate.

To support this claim, the author analyses instrumental temperature records spanning roughly 150 years together with the Group Sunspot Number (GSN) series that extends back to the Maunder Minimum. A quasi‑periodic temperature oscillation of about 60 years is identified in the instrumental data, and the same periodicity is claimed to be present in the SCR proxy derived from flare counts. The paper further introduces a north‑south sunspot‑area asymmetry index, A = (North – South)/Total, and reports that positive values of A (i.e., a dominance of activity in the solar northern hemisphere) coincide with stronger cooling in the Northern Hemisphere.

The author interprets the post‑1975 warming trend as primarily natural rather than anthropogenic. According to the paper, the three‑decade interval 1975‑2007 is characterized by unusually high TSI combined with a marked decline in eruptive solar events (fewer flares and CMEs). This “high‑TSI + low‑SCR” combination, the author suggests, is responsible for the observed warming, implying that the recent climate change is largely a manifestation of the long‑term decline in solar eruptive activity superimposed on a high‑irradiance background.

While the hypothesis is intriguing, several methodological and conceptual shortcomings limit its credibility. First, SCR fluxes for the pre‑satellite era are not directly measured; the study relies on flare counts as a proxy, yet the quantitative relationship between flare magnitude, CME characteristics, and the resulting high‑energy particle flux remains poorly constrained. Second, the detection of a 60‑year temperature cycle is presented without a transparent statistical framework—details on detrending, spectral analysis methods, confidence intervals, and correction for autocorrelation are missing, making it difficult to assess whether the cycle is robust or an artifact of the limited data length. Third, the physical mechanism linking solar north‑south asymmetry to regional cooling is not elucidated. The paper offers no atmospheric or oceanic model that demonstrates how an excess of northern‑hemisphere sunspot area could preferentially enhance particle‑induced cooling in the Northern Hemisphere, nor does it address the role of interhemispheric heat transport.

From the standpoint of mainstream climate science, variations in TSI contribute only about 0.1 % to the Earth’s total energy budget, and the radiative forcing associated with solar cycle changes is far smaller than that from anthropogenic greenhouse gases. The paper’s assertion that the post‑1975 warming is “rather natural” conflicts with multiple lines of evidence: observed increases in atmospheric CO₂, well‑established radiative forcing calculations, and climate model simulations that reproduce the warming only when human emissions are included. Moreover, the claim that a decline in solar eruptive events can offset the warming influence of high TSI lacks quantitative support; the magnitude of SCR‑induced cooling required to counterbalance the greenhouse effect is not estimated.

In summary, the study contributes an interesting perspective by highlighting high‑energy solar particles and hemispheric asymmetry as potential climate drivers. However, the reliance on indirect proxies, insufficient statistical validation, and the absence of a mechanistic model weaken the argument. Future work should aim to (1) obtain more reliable reconstructions of historic SCR fluxes (e.g., from cosmogenic isotopes or ice‑core nitrate records), (2) apply rigorous spectral and time‑series analysis with appropriate significance testing, and (3) integrate SCR‑induced atmospheric chemistry and dynamics into coupled climate models. Only with such quantitative, physically grounded approaches can the relative importance of eruptive solar activity be properly assessed against the well‑documented influence of anthropogenic greenhouse gases.