Ever heard of the Grindelwald Fluctuation?
Your first guess might have to do with Harry Potter, or possibly that it's an episode of The Big Bang Theory, but it's neither. It refers to a sudden, catastrophic dive in average global temperature that occurred in the middle of the already-cold "Little Ice Age," that had started in around 1300 C.E. and didn't really draw to a close until the middle of the nineteenth century. The Grindelwald Fluctuation was a seventy-year period that was cold even by comparison to that baseline. It's named after the Grindelwald Glacier in Switzerland, which grew significantly during that time period. The other results were grim -- crop failures, early (and unusually late) hard freezes, famine, widespread starvation.
I've been interested in the Little Ice Age for a long while, but I hadn't heard about this part of it before. I started looking at the early parts of this Holocene cold period when I was doing my thesis research for my Master's Degree in linguistics, especially apropos of how it affected migrations (and thus linguistic intrusion) into the British Isles. The Little Ice Age, though, had much a broader role in major historical events than simply changing where people went -- the Black Death of the 1340s and 1350s, that ravaged populations worldwide and literally wiped some towns off the map, was probably in part kicked off by falling temperatures and less food driving plague-carrying rats indoors, and into contact with humans.
I also have been fascinated by its effects on northern Europe, largely because of how it kind of stopped Viking/Scandinavian expansion in its tracks. Danes and Norwegians had settled Iceland five centuries earlier, and in fact had even made inroads into Greenland -- then the climate shifted, sea lanes froze over, and weather turned stormy and hazardous, isolating Iceland and destroying the European settlements in coastal Greenland completely. The thought of being stranded, of being the last colonist left alive in a desolate town knowing no one was coming to rescue me, was such a poignant image that it spurred me to write a piece of poetry called "Greenland Colony 1375" that earned me the only award I've ever gotten for my writing -- second place in the Writers' Journal annual national poetry contest in 1999. (If you're curious, you can read it at the link provided.)
The Grindelwald Fluctuation occurred in the midst of what was already the coldest weather humanity as a whole had experienced in recorded history, between the years 1560 and 1630. The cause isn't certain, but may have to do with three huge volcanic eruptions in the Western Hemisphere (Colima in Mexico, Nevada del Ruiz in Colombia, and Huaynaputina in Peru) blowing dust and ash into the upper atmosphere, blocking sunlight and causing the temperatures to fall.
Whatever the reason, it took a bad situation and made it far worse. A paper in The Journal of the Royal Meteorological Society called "Weird Wether in Bristol During the Grindelwald Fluctuation," by Evan Jones and Rose Hewlett (of the University of Bristol) and Anson Mackay (of University College London), considers historical records documenting the experiences of the people who lived through it. The paper is well worth reading in its entirety, so I won't steal their thunder by extensive quotes, but here's one of the records they cite, from the year 1607:
November the 20th 1607 began a frost which lasted till the 8th February following at which time the River of Severn and Wye were so hard frozen that people did pass on foot from side unto the other and played gambols and made fires to roast meat upon the ice. No long trows etc could come to Bristol and when the ice broke away there came swimming down with the current of the tide great massy flakes of ice which endangered many ships that came up the [Bristol] Channel into Kingroad. The continuance of the frost starved a great number of birds, and made corn sell very dear.
Anyone who knows the climate of coastal southwestern Britain can attest that a hard freeze lasting over three months is unheard of. The sharp drop in temperature precipitated not only frigid temperatures but violent winter storms -- there's record after record describing catastrophic floods, windstorms, and snowstorms.
If the whole thing puts you in mind of this century's swing of temperature in the opposite direction, the authors want to make sure that point doesn't escape readers. In the conclusion of the paper, they write:
Links between anthropogenic climate change in the modern world and different types of extreme weather events are now well established. This could increase the costs of weather‐related hazards for about 350 million people across Europe in the coming decades, accompanied by a 50‐fold increase in weather‐related fatalities. Such models fit with anecdotal evidence that the world is already experiencing more extreme weather. Recent examples in the United Kingdom include the record temperature highs of December 2019 and the Severn Valley floods of February 2020...The economic, political and cultural context of the seventeenth century was... very different to that of the twenty‐first century... Yet, despite these differences, the climate and weather of the early modern period provides a reminder of how destructive climate change and severe weather can be in both the short and long term.