https://www.youtube.com/watch?v=fWqKalpYgLo

Solar activity and temperature estimations from 1100 to 1900.

https://science.nasa.gov/science-news/science-at-nasa/2003/17jan_solcon

The solar constant also drifts by 0.2% to 0.6% over many centuries, according to scientists who study tree rings. These small changes can affect Earth in a big way. For example, between 1645 and 1715 (a period astronomers call the "Maunder Minimum") the sunspot cycle stopped; the face of the Sun was nearly blank for 70 years. At the same time Europe was hit by an extraordinary cold spell: the Thames River in London froze, glaciers advanced in the Alps, and northern sea ice increased. An earlier centuries-long surge in solar activity (inferred from studies of tree rings) had the opposite effect: Vikings were able to settle the thawed-out coast of Greenland in the 980s, and even grow enough wheat there to export the surplus to Scandinavia.