Grantville Gazette 37

Climate: The Little Ice Age After the Ring of Fire

In winter 1634, James Byron "Jabe" McDougal "recalled that "the winter of 1631-32 had been quite a shock to himself and his fellow up-timers. Not only were they considerably farther north than they had been when Grantville was in West Virginia, but they were smack in the middle of what up-time historians had called the "Little Ice Age," which had begun some two centuries prior and would continue for another century, give or take. (Robinson, "Mightier than the Sword," Grantville Gazette 6).

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So what was this Little Ice Age? The real Ice Ages were prolonged (as in millennia) periods of pronouncedly colder world or hemispheric temperatures in which the polar and continental ice sheets were of considerably greater extent than in historical times. There have been a dozen or so major glaciations over the last million years. A particularly big one occurred 650,000 years ago and lasted 50,000 years. However, the one that is usually considered the last Ice Age peaked about 20,000 years ago.

So that implies that a little ice age is one that is shorter and milder than that one, yet still noteworthy. Defining when a little ice age begins and ends is a bit tricky. Do you draw the line based on when a particular glacier advances or retreats, when a particular lake freezes or thaws, or when the grapes are harvested? If you rely on mean temperatures, then over how many years do you average them, and to what longer reference period do you compare that moving average? What if the temperature "breakpoints" are different in Iceland than they are in France?

Depending on who you ask, the Little Ice Age began in 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600 or even 1650. There is more agreement as to when it ended; 1850 is the year usually cited, but some would say 1870, 1900, or even 1920.

When people talk about the Little Ice Age (LIA) nowadays, they are mostly interested in the Big Picture: Was the LIA, viewed on some appropriate time scale, a global, a hemispheric or merely a European phenomenon? How much colder was the earth then than it is now? What caused it? Is the Earth warmer now than it was during the "Medieval Warm Period" that preceded the LIA? And to what extent is that warmth attributable to human activity (changes in albedo as a result of deforestation, or increases in greenhouse gases as a result of factory emissions)?

However, for those writing in the 1632 Universe, the Little Picture is what we need: what is the climate likely to be like in Germany, Italy, France, Scandinavia, England and in other areas of interest, each yearover the decade following the Ring of Fire (RoF)? (The RoF occurred up-time on April 2, 2000 and down-time on May 25, 1631 Gregorian calendar.) How does it compare to the climate in living memory, for both the down-timers and up-timers? What practical effect will it have on health, agriculture, transportation, communications, mining, industry and warfare?

In the first part of this article, I will provide some background as to the effects that climate can have on human society.

In the second part, I will try to fill in the Little Picture, based on the assumption that the Ring of Fire hasnot altered world climate; i.e., I can rely on modern reconstructions of historical temperature and precipitation averages in the areas and years of interest.

Finally, in the third part, I will consider the Ring of Fire as a meteorological phenomenon, and speculate about how much and for how long it could perturb weather and even climate.