The solar minimum brings it's own cloud cover to cool the planet. The weakening magnetosphere lets in more cosmic rays which cause cloud formation. No man-made dust, smog or other pollution is needed.

[Galactic cosmic rays are high-energy particles originating from outside the solar system that can impact the Earth’s atmosphere. Our first line of defense from cosmic rays comes from the sun as its magnetic field and the solar wind combine to create a ‘shield’ that fends off cosmic rays attempting to enter the solar system.]