So I am searching through the Web of Science for papers reporting 11 yr (Schwabe) cycles in palaeoproxy data (especially tree-rings) when I find this title, which looks promising:
LUNI-SOLAR 18.6-YEAR AND SOLAR-CYCLE 10-11-YEAR SIGNALS IN CHINESE DRYNESS WETNESS INDEXES
The abstract in WoS is, well, abstract
The pilgrim fathers of the scientific imagination as it exists today are the great tragedians of ancient Athens, Aeschylus, Sophocles, Euripides. Their vision of fate, remorseless and indifferent, urging a tragic incident to its inevitable issue, is the vision possessed by science. Fate in Greek Tragedy becomes the order of nature in modern thought. …the essence of dramatic tragedy is not unhappiness. It resides in the solemnity of the remorseless working of things. This inevitableness of destiny can only be illustrated in terms of human life by incidents which in fact involve unhappiness. For it is only by them that the futility of escape can be made evident in the drama. This remorseless inevitableness is what pervades scientific thought. The laws of physics are the decrees of fate.
But when I go to check the paper, I find a much more conventional abstract
Power spectrum analysis of 81 long and 202 short Chinese dryness-wetness indices yields evidence for two peaks with periods near 18.6 and 10.5 years, both of which are statistically significant at confidence levels of 99.9 per cent. They are identified as induced by the 18.6-year luni-solar, Mn, constituent tide and a 10–11-year solar cycle, Sc, variation in the Sun’s luminosity of the order of 0.1 per cent. Amplitude and phase of Mn wavetrains are highly non-stationary with respect to both time and geography; in particular, abrupt 180° phase changes in wave polarity are often observed. Amplitude and phase of Sc waves are also highly non-stationary, with those in northern China out of phase with waves in the south since 1895 (they were in phase from 1815 to 1845). For the 202 short records variance contribution of the two signals to total variance in raw data varied from 6 per cent to 53 per cent, with a mean of 22 per cent, again demonstrating their extreme non-stationarity. Construction of a dry and very dry drought index (DVDI) shows that since 1470 by far the most prolonged, continuous, and serious drought (due to constructive interference and concomitant high amplitudes of the two waves) occurred from 1633 to 1643; the Ming Dynasty collapsed in 1644 and, in agreement with Hameed and Gong (1990), it is concluded that this climatic disaster was a causal factor in the fall of the Ming Empire.
The abstract in WoS is actually a long quote from Alfred North Whitehead.
So far I have about 100 candidate papers (sometimes it is not clear from the abstract if the paper is reporting Schwabe cycles or some longer term solar variability).