Temperature, of course, is only one of the two principal dimensions of climate; the other is precipitation. Pauling reconstructed precipitation across Europe in 1500-1900, and his 1630-39 results are in Table 2-8. Fig. 3 compares the average for 1630-39 to that for 1990-99.
I provided the standard deviation, as well as the average, for 1630-39, and it is apparent that the annual variation from year to year for a given season was fairly small. However, because of the North Atlantic Oscillation, it's not unusual for northern Europe to be dry when southern Europe is wet, and vice versa.
Reconstructions are available of the average sea level and upper air pressure (in millibars) for each season in 1500-1658, and thereafter monthly (Luterbacher2002). For reasons I will explore in part III, this pressure history is more likely to get buffeted by the RoF than the temperature data, so don't put a lot of faith in it. Still, the patterns shown will remain plausible patterns. For 1630-4 and 1636-39, we had a winter high near the Azores and low near Iceland, with these highs and lows weaker in the other seasons. The Icelandic Low was distinctly weaker and displaced in the winter of 1635.
Sunspot number normally varies according to a somewhat irregular 11-year cycle. However, there have been several periods of prolonged depression of sunspot number, notably the Sporer Minimum (1460-1550), the Maunder Minimum (1645-1715), and the Dalton Minimum (1790-1830), all of which correlate with cold temperatures. In the old time line, of course, no one had to worry about radio communications during these minima!
While it may sound as though we don't have to worry about the Maunder Minimum yet, that's not so. You see, the sunspot number is already on the decline. The total number of sunspots in the period 1630-1640 (eleven years) was 185.4. In contrast, in 1980-1990, the total was 956.1. The period 1645-1715 was simply worse, with no sunspots at all in most years.
So the decade of the 1630s may be considered the 'slippery slope' down to the Maunder Minimum. And that means that (with the exception of 1638-9 and 1642) we will be facing progressively greater limitations on the range of radio communications.
The great circle route is the shortest distance between two points, but it can require you to sail at dangerously high latitudes. While the cold can cause frostbite and sap strength, the greater danger is from sea ice.
In the North Atlantic, the principal pathways by which ice can descend from the Arctic Circle are the Davis Strait and Baffin Bay between Newfoundland and Baffin Island to the west and Greenland to the east, the Denmark Strait (Greenland Sound) between Greenland and Iceland, and the Norwegian Sea between Iceland and Norway. Nowadays, Arctic sea ice reaches its maximum overall extent in March (Polyak), and I suspect this was likewise true in the 17th century. However, note sea ice can expand in the Greenland sound while contracting in the Davis Strait, and vice versa. In a 'normal' severe year, the ice could surround Spitsbergen and bisect Iceland. It only rarely reaches the south coast of Iceland. (Ogilvie).
Looking at the documentary evidence-based sea-ice index for Iceland, filtered through a 15-year low-pass filter, the 1630s and 1640s exhibited values under 2, while the filtered index climbed above 5 in the 1780s, 1810s, and 1830s. (Ogilvie). So the 1630s are not especially bad insofar as sea ice is concerned, although in one of the years (1632? 1633?) it jumped to level 6. An earlier (Koch 1945) study says that there was drift ice at the coast for 24 weeks in 1633, 26 in 1638 and 17 in 1639 (LambCPFF 583). Consistently, GroveLIAAM (22) states that 'the 1630s . . . which were cold on land, saw little sea ice. . . .'
For the waters around Greenland, based on GISP2 ice core chemistry, the sea ice levels increased more or less steadily throughout the first half of the 17th century. However, the levels in the early- and mid- 19th century were higher (Dugmore Fig. 7).
Jabe McDougal's musings continued, 'After the high school had been saved from the Croat raiders, there had been a wave of interest in Swedish and Scandinavian history. Jabe had learned about the Little Ice Age and its presumed role in the death of the Viking colonies in Greenland.' (This role is now considered debatable, see e.g. Mann.)
While we aren't interested in colonizing Greenland, it does have resources of interest. In year 1633 of the new time line, the Dutch metal and armament magnate Louis de Geer sent an expedition to Ivigtut (61o12'N/48o10'W) in southwest Greenland, at the mouth of Arsuk Fjord, to search for cryolite (the flux needed for efficient electrolytic production of aluminum metal from aluminum oxide) (Mackey, Kim, 'Land of Ice and Sun,'
Well, maybe. But as Kim pointed out when the story was in slush, while it was certainly cold, there was evidence that in the 1630s, it was no colder than when cryolite mining began (1854). Production was 14,000 tons in 1857-67; 70,000 in 1867-77 (Johnson's).
While I don't have air temperatures for Ivigtut per se, ice core data for Site J (66o51.9'N/46o15.9'W, 2030m) in South Greenland, inland, was used to reconstruct June temperatures for Jakobshavn (69o13'N,51o6'W,30m) on the west coast. This was -0.11oC in 1633, 0.08 in 1634, 0.30 in 1635, and remained
In the 1632 universe, we also have a Danish colony on Hudson Bay founded in 1634. We can glean a bit of climate information from the reports of the expeditions that visited Hudson Bay or its southward extension James Bay. Hudson entered Hudson Bay in early July and was frozen into James Bay on November 10, 1610. Luke Fox entered Hudson Bay in late May, 1631. Thomas James entered Hudson Bay on July 16 and James Bay in early September, 1632.
Otherwise, unfortunately, we must decide which part of the post-1700 (Guiot) or 1750 (Catchpole; Ball) data is most analogous to the 1630s and 1640s.
The wetness/dryness index (norm 10) for Russia (35oE) in the high summer (July-August) is 11.5 for the 1630s and 7.5 for the 1640s. LambCPPF 562). The winter mildness/severity index ( norm zero) was -10 for the 1630s and -36 for the 1640s (the worst value over 1100-1969). (564). Brooks (249) says 'In the 1640s . . . severe cold was reported for every month of winter, making this the coldest decade in Russian history since the twelfth century.'
For an overview, a good place to start is the North American Drought Atlas, which includes Palmer Drought Severity Index (PDSI) values, for summer 1634-1639, based on tree-ring data (Cook). You can see that the northeast suffered a drought in 1634, which deepened in 1635. California was wet in 1635-6, but it and indeed the entire Pacific Northwest dried up in 1637-39. Mexico was generally quite wet. Unfortunately, rainfall patterns are likely to be perturbed by the RoF. Hence, take Fig. 4, which shows the pattern for 1635-37, with a very large grain of salt.
Figure 4
There is also a tree-ring reconstruction of annual and seasonal temperature and precipitation anomalies for the USA from 1602 on. From this we can see, for example, that in the northeast, both winter and summer 1634 and 1638 were relatively cool, while 1635-37 were characterized by relatively warm summers and relatively cold winters (Fritts).
