Which parts of Europe are unusually hot and which are unusually cold is very strongly influenced by the position, areal extent and persistence of the high and low pressure areas (see North Atlantic Oscillation) and the position and strength of the jet stream. Stagnant (blocking) patterns lead to persistent weather conditions that influence monthly and even seasonal averages. On the west side of a stationary NH high, warm air is pushed north, and on the east side, cold air is dragged south. So you may be warmed or cooled depending on where you stand. Moreover, a slight shift in the location of the blocking pattern from one year to the next might mean that you face extreme cold in the first year and extreme heat in the second (LambWCHA 110).
The place of greatest interest to the up-timers is, of course, the location in Thuringia where the RoF deposited Grantville. The center of the RoF was at approximately 11o16' east longitude, 50o40'12' north latitude. The closest Luterbacher grid point is 50.75N, 11.25E, and the reconstructed seasonal temperatures for this location are in Table 2-5A (with comparison to pre-RoF Grantville at the bottom of the table).
It can be seen that in OTL 1620-49, the growing season (April-September) was probably about 4- 5oC. colder than in 1971-2000 Grantville. If extremes moved downward the same amount, that probably wouldn't shift Grantville into a new plant hardiness zone (that would require an 18oC change.)
Magdeburg is at 52o07'N, 11o38'E, and the closest grid point is 52.25N, 11.25E. The data for that grid point are in Table 2-5B.
It is possible to extract the reconstructed temperatures for other locations in Europe, too, given their latitude and longitude. The necessary data set and format information are here:
http://www.cru.uea.ac.uk/cru/projects/soap/data/recon/#luter04 Please note I had to write a program to extract the data, because Excel can't import 18,000 columns of data. . . .
Unfortunately, I don't have gridded monthly temperature reconstructions covering the 1630s. Mark Twain once said, 'there are three kinds of liars: liars, damn liars, and statisticians.' We can make an educated guess as to what the monthly temperatures were, using statistics for other time periods. There are a number of ways that this can be done. I assumed that the relationship of monthly to seasonal temperatures for Grantville was the same as for Central Europe.
Or, in mathematical terms,
Grantville average for that month= Grantville average for that season (from LuterbacherTemp) + adjustment, where the adjustment was Dobrovolny's central Europe average for that month – central Europe average for that season.
Table 2-6A provides my reconstructed monthly temperatures for the location that Grantville was transported to. For convenience, I also repeat the climatological normals for Fairmont, West Virginia.
Bear in mind that these monthly numbers, even if accurately reconstructed, are the likeliest climate statistics to be corrupted by the 'butterfly effect' of the RoF. So that's another good reason to view them as general indications rather than gospel truth.
What I thought most noteworthy about them was how fast temperatures dropped off during autumn and rose during spring.
Table 2-6B provides the average and standard deviation, over 1766-1850, of Luterbacher's reconstruction of monthly mean temperature at the same location. These, of course, reflect a different time period, but they save us the trouble of trying to convert temperature anomalies into absolute temperatures.
We can estimate the number of growing degree days for a given location and year, for whatever base is appropriate to a particular crop. (Schenkler; Thom). Using the estimated monthly means and standard deviations from Table 2-6A, then by Thom's method we get the dramatic results shown in Table 2-7.
We also can make some educated guesses as to
Unfortunately, there's a catch: the DTR can change as the climate changes. In particular, 'the blocking action of greenhouse gases would be most effective where outward radiation was most important for cooling the Earth: warming would come especially at night' (Weart). So the DTR of the late-twentieth century is probably smaller than that of the seventeenth, when greenhouse gases were at lower concentrations and thus had less of an upward influence on nighttime temperatures.
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The USDA plant hardiness zones are defined on the basis of the climatological norm of the annual minimum- the lowest daily minimum recorded during the course of the year. Unfortunately, to calculate that, by Monto Carlo methods, we need to know not only the monthly mean and standard deviation for (at least) January, but also the correlation of one day with the next.
Plant Hardiness Zone Maps have been created for modern Europe that use the same scale as the USDA maps (Heinze), and based on 1881-1930 data (although Lorek says that including 1931-1960 data would have an insignificant effect); Grantville post-RoF is in zone 6b (average January minimum of 20.5-17.8oC, -5 to -10oF) and Magdeburg in 7b (14.9-12.3oC, 10 to 5oF).
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A change in climate may simply shift the mean temperature, and leave the variability intact. Or it can alter the variability, too. If for example, it was not only colder in the 1630s than in the 1990s, the variability increased, then the likelihood of frosts would be much greater than you would expect by just considering the mean. To complicate matters further, there's no guarantee that the 'cold' and 'warm' tails of the distribution will be affected by the same amount or even in the same direction.
Scientists have looked at both twentieth-century observational data (Kurbis, Moberg, Easterling, Karl, Michaels) and runs of global climate models, and about all I can conclude from this is that it's not safe to assume that the variability of temperature was the same in the early-17th century as it was in the modern period. Unfortunately, I have no easy way to predict how it was different and therefore I must just admit that this is something the authors may easily play around with.
