The extraordinary cold spell was probably strengthened and lengthened by the resulting increase in sea ice at high latitudes, as well as an unusually low number of sunspots in the middle of the 7th century. (sciencemag.org)
While solar output typically goes through 11 - year cycles with high numbers of sunspots seen at their peak, we are currently approaching the peak of «Cycle - 24» with numbers running at less than half of those observed during other 20th century peaks. (cfact.org)
The forecast is for cycle 25 to be smaller in number than cycle 24, shown to the right of this photo, which is the smallest number of sunspots since cycle 14 that reached its peak around 1912. (ddears.com)