One of five THEMIS probes that study these issues
We normally say that the solar activity has an 11-year periodicity but the even and odd cycles differ by the sign of the magnetic field and their effects on the Earth may differ due to the Earth's own magnetic field. So the underlying periodicity is 22 years. In fact, a 20+ year temperature (or related) signal has been observed in tree rings. It was puzzling because people thought that only the absolute value of the Sun's magnetic field should matter, and the latter had a 11-year periodicity.
However, already in 2007, we mentioned a paper about a possible role of interstellar dust as a climate driver: this dust was proposed to realize the 22-year cycles. Something of this sort is probably happening. It is not exactly clear which of the effects related to the magnetic fields and magnetic storms and auroras etc. are going to be crucial for the temperature.
In closely related news, the Earth's ionosphere dropped to a new, unexpected low.
Via Solar Cycle 24 and Watts Up With That