A new paper published in Chemical Geology finds the Iberian Peninsula was 'rather more humid' than today from 10,000-6,000 years ago including the Holocene Climate Optimum. The authors also find "Saharan dust [over Western Europe] is driven by solar forcing and 1.5–2.0 thousand year cycles," which affects regional climate due to dust aerosols in the atmosphere.
According to the paper
Effective humidity reconstruction indicates wetter conditions during the early Holocene and progressive aridification during middle–late Holocene time, boosting abrupt changes in the lacustrine system. Cyclostratigraphic analyses and transport mechanisms both point to solar irradiance and aridity as major triggering factors for dust supply over Western Europe during the Holocene.Data from the paper shows the Iberian Peninsula was much more humid during the early-mid Holocene [past ~11,000 years] in good agreement with solar insolation, and per the Clausius–Clapeyron Relation, warmer air can hold more water vapor/humidity. The data shows humidity decreased to the lowest levels of the Holocene during the Little Ice Age and has recovered slightly since to the end of the record in 2006.
Thus, the data suggests the Sun drives humidity/aridity and dust transport, both of which have large effects upon climate and may add to many other solar amplification mechanisms described in the scientific literature.
Note: Another new paper claims dust from distant deserts can increase atmospheric heating by a factor of four times.