Between 1300 and 1850, the Earth experienced a Little Ice Age whose cause to this day is not known.
A blog post at Interesting Engineering has more details including the consequences and some paintings from the period. The causes listed are interesting:
Causes
The causes of the LIA are still not known, while potential candidates are reduced solar output, changes in atmospheric circulation, and volcanism.
Low sunspot activity is associated with lower solar output, and two periods of unusually low sunspot activity occurred during the Little Ice Age: the Spörer Minimum (1450–1540) and the Maunder Minimum (1645–1715), which is named for astronomer E.W. Maunder who discovered the absence of sunspots during that period. Both of these coincide with the coldest years of the LIA in parts of Europe.
Another possible candidate is a reversal of the North Atlantic Oscillation (NAO). This is a large-scale atmospheric-circulation pattern over the North Atlantic and adjacent areas. During its “positive” phase, the track of North Atlantic storms is centered over the British Isles and Northern Europe. During its “negative” phase, cold Arctic air from Russia moves over northern Europe.
A final candidate is volcanic eruptions which propel gases and ash into the stratosphere, where they reflect incoming sunlight. In 1783, Iceland’s Laki volcano erupted, and in 1815, the Tambora volcano on Sumbawa Island erupted.
I am voting for low sunspot activity. Your thoughts?
The Next Grand Minimum 
My guess is that the reasons for the Little Ice Age are multiple, and the reasons listed above probably all contributed to a cooling earth. It’s never really just one thing. Volcanism has certainly been correlated to cooling all through the earth’s geologic history, but now it too is being considered as a symptom of the grand solar minimum. I feel strongly that the sun is still the main driver of climate here on earth…and everything else just contributes to our climatic experience. However, CO2, which is considered a “trace” greenhouse gas, only contributes a very small fraction toward any climate variation on the planet.
I have been wondering if solar CMEs could be earthquake and volcanism triggers. We have earthquakes, moonquakes, and marsquakes. Could they all have a common trigger mechanism? Thoughts?
Could be. As water weight shifts from the oceans to mountain glaciers, the stresses in the crust will change. That could plausibly trigger faults to slip as the stress builds. Crustal weight on the core would shift as well possibly increasing pressure in magma pools.
http://2020ce.blogspot.com/2017/01/un-mondo-sconosciuto-sotto-un-sole.html
This link may be useful to you.
Thanks for the link. This was a fascinating read and deserves more study. Recommended reading.
Couple of considerations; during low solar activity periods the whole atmosphere contracts, jet streams distort – as we have at present – they should have moved further towards summer positions than they are at the moment. Cyclonic lows will drag polar air further south, throw tropical air further north (talking Northern hemisphere) which will, after initial warming, increase overall heat loss especially if it happens over some years – normal entropy.
Second point, changes in the solar induced geomagnetic environment may well interact with earth’s magma movement and result in increased tectonic stresses and activity. Increased volcanic activity during minima seems well established.
Reblogged this on Climate- Science.