Grantville Gazette 37

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If we consider just the temperature column, it's clear why the up-timers feel a chill in the air. However, the coldness ranks (30-362) provide some perspective. And it's worth comparing those temperature to the averages (Table 2-2B) for each century, for the Maunder Minimum (1645-1715), the whole LIA (1500-1850), and the modern period (1851-2004).

We can see that only three years were below the average (8.2^oC) for the LIA. The worst year of all (1635) was the 30^th coldest year for the period studied (1500-2004). It was not the coldest year in living memory; that was probably 1573 (7.0^oC, 2nd coldest), and down-timers will also remember 1587 (14^th), 1595 (10^th), 1600 (5^th), 1601 (8^th), 1608 (6^th), and perhaps also 1565 (13^th) and 1569 (9^th).

So, yes, we are in the LIA-but not in the worst decade, by any means.

Climate Reconstructions: European Seasonal Average Temperatures

There are several references to the severity of winter in 1632 universe canon. Watching TV in 1633, Joyce and Gary find that 'the news was about broken armies, new business, and, of course, the weather and what the little ice age meant to their future.' (Huff and Goodlett, 'Wish Book' Grantville Gazette 12). In January 1634, Eric Krentz tells Thorsten Engler, 'I always hated January even before an up- timer told me we're in the middle of what they call 'the Little Ice Age.' ' (Flint, 1634: The Baltic War, Chapter 14). Later, in late March 1634, Admiral Simpson is 'a bit surprised that the river [Elbe] hadn't frozen, although intellectually he'd understood that the past winter hadn't really been as cold as it had sometimes felt, Little Ice Age or not.' (Chapter 31). In Flint and DeMarce, 1635: The Dreeson Incident, we are told that 'Winter in Thuringia during the Little Ice Age encouraged the layered look.' (Chap. 41).

So, how did LIA winters (and other seasons), compare to those the up-timers would have been acclimated to, and just how bad were the 1630s as compared to other parts of the LIA?

We define the seasons as DJF (winter, December-January-February, and I assume that winter for 1630 starts with Dec. 1629), MAM (spring), JJA (summer) and SON (fall). Table 2-3provides the reconstructions for each of 1630-1639, the actual values for 1999 and 2000, and averages of values for the decade 1630-39, the 30-year period 1620-1649, 1645-1715 (the Maunder sunspot minimum), 1500-1850 (LIA) and 1851-2004 (Post-LIA). The coldest (bold blue) and warmest (italic red) winter, spring, summer, fall and entire year are marked.

I have calculated, but not shown, the seasonal coldness ranks. Looking first at winter (DJF), 1635 was the 32^nd coldest in the study period. The next worst was 1637, ranking 129^th. The mildest winter of the decade was that of 1633, ranking 408^th. The LIA mean was -1.125C, so five years were better and five were worse, and the mean for our decade was a bit milder.

The springs (MAM) ranged in rank from 62^nd to 459^th coldest, the summers (JJA) from 92^nd to 424^th, and the falls (SON) from 60^th to 372^nd. For all three seasons, the mean for our decade was higher than the mean for the LIA.

Surprisingly, the mean for summer 1630-1639 was even higher than the mean for the post-LIA (1851-2004) period, although of course still cooler than the summers of 1999 and 2000.

We are lucky to have missed 1628, which was the thirteenth coldest summer (16.8^oC) of 1500 -2004.

Climate Reconstructions: Central European Monthly Average Temperatures

Monthly temperatures have been reconstructed for central Europe in 1630s, based on documentary evidence (mostly from sites in the present Germany, Czech Republic, and Switzerland). Unfortunately, these are available just as anomalies, that is, the difference between the actual temperature and the average(s) for the base period 1961-1990 (Dobrovolny). I emailed Dr. Dobrovolny, asking him for the base temperatures, but he didn't reply. So I used the KNMI Climate Explorer to download the CPC GHCN/CAMS t2m analysis (land) data, gridded at 0.5° intervals, and calculated the 1961-1990 base for central Europe myself. I assumed that Dobrovolny defined central Europe the same as his coworkers did in LuterbacherSLP.

In Table 2-4, I show first my derived monthly temperatures for each year of 1630-39, and the average and standard deviation for the decade. Next, I provide my 1961-99 base numbers. There're no guarantees that Dobrovolny had exactly the same base averages; his region and his modern data could have differed from mine. But since I stated the bases I used, you can reconstruct Dobrovolny's anomalies by subtracting them out. Finally, I present the mean and standard deviation for the period 1766-1850, from Luterbacher's monthly gridded reconstructions.

Please note that with the exception of 1630 and the first four months of 1631, this monthly data is subject to perturbation by the RoF. Since it's time-averaged data, the impact won't be as severe as for daily weather, but there will be some effect.

Climate Reconstructions: Mapping Post-RoF European Seasonal Average Temperatures

Of course, pan-European averages are all well and good, but different parts of Europe would no doubt fare differently. Fortunately, Luterbacher's climate reconstruction provides reconstructed seasonal temperature for each point on a 0.5 degree by 0.5 degree grid, over the range 25W-40E longitude; and 35N-70N latitude.

It's said that a picture is worth a thousand words, and I have created some revealing images from Luterbacher's gridded temperature data. Using Climate Explorer, I have compared the decade 1630-39 with 1990- 99. The figures compare the decades for (Fig. 1A) the entire year, (1B) winter, (1C) spring, (1D) summer and (1E) autumn.

And using the National Climatic Data Center's visualization tool, I have created comparisons of the coldest and warmest winters (2A), springs (2B), summers (2C) and autumns (2D) of the 1630s. Note that each season has a different temperature scale:

Winter (DJF): coldest 1635, warmest 1632, scale -20 to +10C;

Spring (MAM): coldest 1635, warmest 1636, scale -5 to +25C;

Summer (JJA): coldest 1630, warmest 1637, scale +5 to +35C;

Fall (SON): coldest 1635, warmest 1630, scale -5 to +25C.