Mann and Jones have a new post at realclimate discussing warmth at Svalbard, an island archipelago north of Norway. May temperatures are very warm there. They say that the differences are 5 standard deviations based in i.i.d. We’ve talked about the inappropriateness of i.i.d. assumptions in the context of Rasmus (BTW what ever happened to Rasmus over there? – I predicted that Gavin would ice him and this seems to have happened.) Terry drew this article to my attention. He attempted to post a comment asking about autocorrelation, but this seems to have been censored by realclimate. After all, that would be a “serious” discussion.
Mann and Jones say that “models show” "polar amplification” (although I didn’t notice any discussion of declining temperatures in Antarctica.) I’m not going to go through the statistics, but I thought that I’d post up some interesting comments from Hubert Lamb  on the northeast Atlantic.
Lamb’s abstract says:
“Variations must take place in the ocean circulation when the general wind circulation varies. There are hints even within recent years that variations in the ocean between Iceland and Scotland and Norway can be big. The area has been regarded as the main path of the warm saline North Atlantic Drift water heading towards the Arctic; but when the polar water occasionally intrudes from the north, sea surface temperature is liable to fall by 3 to 5 deg C and presumably by more than this when, as in 1888, the ice advanced to near the Faeroe Islands.
The reconstruction of the situation between AD1675 and 1705 resulting from this study suggests a probable mean departure from modern values between the Faeroes and southeast Iceland amounting to about –5 deg C and at the climax in 1695, the polar water seems to have spread all around Iceland; across the entire surface of the Norwegian Sea to Norway and south to near Shetland. Support for this diagnosis is found in a considerable variety of reports of environmental conditions existing at the time in Scotland, south of Norway and elsewhere. The enhanced thermal gradient between approximately latitudes 55 and 65 N during the Little Ice Age, which this result indicates, offers an explanation for the occurrence in that period of a number of windstorms which changed the coasts in various places and seem to have surpassed in intensity the worst experienced in the region in more recent times.
Lamb’s article itself is an interesting discussion of wind circulation regimes in the north — a continuing theme in Lamb’s work. Lamb points out that there is a far larger flow of water poleward through the Atlantic than the Pacific (about 10 times more according to the estimates of the time). Well before Broecker’s Conveyor Belt, he pointed out interestingly that the coast of Brazil is like a wedge in the course of the South Equatorial Current and a shift of only 1-2 deg of latitude of this current to the nose of Brazil would affect the warmth and volume of the Gulf Stream (citing Brooks 1949), reporting that shifts of 1-2 degree latitude in wind circulation do occur.
He states that the volume of water transported southward by the East Greenland Current can vary by a factor of 10 (a normal distribution– anyone?). The East Iceland Current, the branch which heads southward around the east side of Iceland, is said to vary greatly both in volume.
Lamb reports that the Faeroe Islands (62N, 6.8W), which are to the southeast of Svalbard (73N, 20E) have a long series of SST temperatures, which “seems to be an interplay between the contrasting water masses in this sensitive area” and that the differences in 5-year means was twice as great as in C England air temperatures.
Lamb suggests that the cod fishery can serve as a proxy for SST since the “abundance of cod seems to be limited by the 2 deg C isotherm”. He then describes failures of the cod fishery in the Little Ice Age, relating this to changes in ocean circulation. He mentions that the worst years in the region seem to have been the 1690s, particularly 1695 when the sea ice surrounded Iceland.
He says that “between 1675 and 1700, the water temperatures prevailing about the Faeroe Islands presumably were on overall average 4 to 5 deg C below the average of the last 100 years, an anomaly 4 or 5 times as great as that shown by the thermometer observations in central England where the coldest decade (1690s) averaged about 1.5 deg C below the warmest decades in the earlier part of this century”
In passing, some of you may remember the peculiar truncation in MBH98 of the Central England temperature series to exclude the late 17th century – the very period which Lamb ascribes as being the worst of the Little Ice Age. In the Mann Corrigendum, he justified this on the basis that he used data from Bradley and Jones 1993. But this simply passes the question on: what business did Bradley and Jones 1993 have in truncating the late 17th century portion of this record – in an article purporting to show the non-existence of the Little Age?
Lamb also reported interesting information from travellers about depressed snowlines in Scotland in the 17th and 18th centuries, saying that “the apparent lowering of the snow line by 300 to 400 m in the Little Ice Age would imply an average temperature level 2 to 2.5 deg C below that of the mid-20th century, an anomaly rather more than twice as great as central England, but one that could be explained by the lower temperatures which we derive for the ocean within 500 km to the north”. He cited tree ring estimates from Norway.
He notes that Stolle 1975 had deduced that already in 1577 the Gulf Stream was turning east away from the American cost on a more southern track than has been normal in this century and suggested that movements continued even further south. For Greenland, he suggests (Lamb 1977) that the water temperatures in the fjords of southwest Greenland around 1000 AD at least sometimes reached values not less than 4 deg C warmer than the in the warmest part of the present century, concluding that this must have characterized the open seas occupied by the southernmost extension of the East Greenland Current. He then dates the advance of sea ice and decline of Greenland, with difficulty commencing by 1250 and regular communication ceasing by 1410. In contrast, he says that in the eastern part of the Norwegian Sea, there was little adverse impact until about 1550.
So what do we have here: in the Faeroe Islands, Lamb says that the fluctuations are far more marked than in Central England. Svalbard (73N, 20E) is to the northeast of Faeroe (62N, 6.8 W). So there’s every reason to believe that it would have fluctuations on the same or greater scale as Faeroe. So do high May temperatures in Svalbard prove that temperatures in this region were warmer than in the MWP? If so, then why haven’t the treelines in Finland and Siberia reached MWP levels? OK, maybe there’s a delay and maybe the treelines based on present temperatures will reach MWP levels. But they haven’t so far. So there must have been a sustained period of warmth in the past which permitted trees to thrive at higher altitudes in the MWP "locally" in Siberia, Finland and California and go further north in the Canadian Northwest Territories.
Lamb is a terrific read. He’s a fine writer with an eye for detail. The only reason his work fell out of favor was because it supposedly became obsolete with pseudo-quantitative Mannian multiproxy studies, which claimed the ability to make annual reconstructions. Now they seem to be resiling from that and Wahl and Ammann say that they are only trying for “low-frequency”. In any event, if you believe, as I do, that the entire Hockey Team corpus is of little merit, then it’s time to re-read Lamb and see what he actually says.
Reference: Hubert Lamb, 1979. Climatic variation and changes in the wind and ocean circulation: the Little Ice Age in the Northeast Atlantic, Quat. Res 11, 1-20.