F3  Discussing the kick off to global cooling
Draft 28 April 2011

 F31 The North Atlantic is not the only but the dominant factor

 The North Atlantic is not alone on the world, and the kick off of global cooling need not necessarily be the solitary source, although in the Northern Hemisphere this ocean body is by far the most relevant weather maker. Only in some distant the Arctic Ocean, and the North Pacific follow, as the ocean regions of the Southern Hemisphere. 

 Before putting the focus entirely on the North Atlantic, few words about the other two oceans areas north of the equator. Both are subject to special sections. The next concerning the North Pacific is covering the naval war period from 1942 to 1945, the other the Arctic from where a stark warming started at the end of WWI in winter 1918/19, which has a strong correlation with the naval war in Europe from 1941 to 1918. That raises immediately the question concerning the cooling 20 years later, which I can only raise, but not elaborate.

About the Arctic any consideration, which starts with Artic warming two decades  already requires with a contributing factor of naval war, would logically expect a significant sign, either increase or reversal. All data records show that there is a very pronounced sign towards reversal. But trend  change did not came as a bang as in winter 1939/40, and it did not came to a steep and long lasting decline. Although the timing fits well with the naval war thesis, it would require another type of research to bring more light into the matter, as done here and deemed helpful to support the thesis with reasonable mean and consideration.  

Figure 4: The Global Cooling vs the Warming (1919-1939)

About the North Pacific With regard to the relevance of the North Pacific in the winter temperature structure of the Northern Hemisphere north of latitude 30°N (Shanghai, New Orleans, Cairo) I can only offer my personnel opinion. The North Atlantic is by far the major contributor to the relative high level of temperature throughout the Northern Hemisphere during the winter season, followed in quite some distant by the North Pacific (30° to 60°N), and the  Arctic Ocean. The continental land masses, particularly those covered with snow contribute the least. The point to make is, that a significant cooling during the winter season over the North Atlantic is showing up in the North Pacific as well. Due to the Gulf Stream and its reach with the West Spitsbergen Current up to the Arctic Ocean, the heat potential is driving factor of Northern Hemisphere winter weather. It was the force that generated and sustained the early Arctic warming  (1919-1939), which will be subject to the final chapter. 

F32 The Sea Surface Temperature issue

 One of the weakest points in climate research is the lack of reliable sea temperature and salinity data, across several sea levels and over many decades. A climatic research that is not capable to understand that these data in high number and frequency are absolute paramount to undertake reliable climatic research. The current material available is hardly more than an initial approach, and rarely sufficient for in-depth research. That applies generally for historical data, including the data taken during war times, as frequently expressed and underlined by special investigation (Bernaerts ,1976 & 1977). As far a sea-surface data (SST) have had their value for weather forecasting, which is no way questioned, it does not mean that 
Fig.5
they have a similar value for analysing climate change pattern. At best they may indicate a trend, if carefully analysed  , and applied. That is in no way possible for SST taken during the times of major wars. Any ‘adjustment’ is speculative. The most one might get from a data series is a trend. 

The SST trend in the North Atlantic region changed around 1940. Until than there had been a significant warming trend (Figure ), which corresponds with the situation throughout the Northern Hemisphere and on a global basis (see Sec. F1, Fig.1). What seems necessary to note is the margin of change one is talking about. It is at most one degree over a time period from around 1900 to 2000, based on the data for the North Atlantic (Figure ).  As the error margin for each measurement taken was in the range of about 0,5° to 1°C, one should doubt the usefulness of such data for climate research highly. 

 From the available SST data set it seems difficult to follow the recent opinion of Thompson et al (see F12), that: “the hemispheric differences in temperature trends in the middle of the twentieth century stem largely from a rapid drop in Northern Hemisphere sea surface temperatures of about 0.3 °C between about 1968 and 1972”. The most significant trend change happened between about 1940/42, which should be explained first before considering a subsequent change at the end of a three decade cooling period. 

F33  What can NAO tell?

 The North Atlantic Oscillation (NAO) is not really useful in our case, even though it is said that the sequence of cold winters in the 1940’s correspond to variations of the NAO Index. This would corresponds to the similar cold conditions in the 1960s, and the warmer conditions in the 1990s. The NAO Index relates to the speed of mid-latitude westerly winds, and is measured by the difference between pressures at two places at much the same longitude but widely separate latitudes (Iceland, 65°N,  and the Azores, 40°N). Whether this analytical concept can

Fig.6   
be made fruitful for exploring the influence of the WWII years is hardly possible to be answered here, as the 1940s was still not the time to collect the relevant data. But that intelligent research may nevertheless bring about interesting, if not evidential correlation, is the observation by James Bhend (A2-9), that there had been a strong increase of cyclonic activities during the WWI and WWII period. 

F 34  A link between the North Atlantic and Europe?

 This investigation has no doubt about that, a position recently confirmed by Juraj Vanovcan. In an essay at “Watts Up With That” (WUWT)[1], 26 September 2010, he wrote: 

• “The decadal oscillation in North Atlantic sea surface temperature is the driving force behind observed variations in European climate during 20^th century. Long-term North Atlantic SST trend is well correlated to European temperature station record”. 

Fig.7

To under line this point he compared the data record between NA-SST and the air temperature in Europe in a graphic (Figure ), with the explanation:

·        “the North Atlantic SST record with the European ground stations within 40-70N and 10W-30E is well correlated with the Atlantic SST changes, and lags the SST record by some 5 years. It is thus obvious, that it is the Atlantic decadal variability, which dictates the European climate.”

Although Vanovcan recognises clearly “that there has been pronounced cooling period since 1940 until 1980, which completely erased the early century warming against the 19^th century average”, he is not aware of the deep decline of air temperature in Europe (which I indicated in Fig. ). Despite this reservation the paper is worth a full read and Anthony Watts indicated it as a ‘must read’, commenting that: “The conclusion from this essay is that the oceans drive the temperature of the atmosphere, not the other way around.” 

 F33   The temperature-drop issue

 The ultimate starting point remains the question what caused the air and sea water temperature across the North Atlantic region to decrease over three decades. Was it an ocean issue alone, or did the Battle of the Atlantic contributed? Fact is that the temperature coincided in perfect timing with the naval war activities, as indicated by a number of graphics in this section. Fact is also that the water of the North Atlantic circles the basin, in a rhythm of about four years. A letter bottle released off Cap Hatteras needs less than half a decade to show up here again. When Western Europe faced the late and sever winter 1946/47, the water body was already in the midst of the second full circle, by a starting point in 1940.

This is reflected in a comparison between a maritime country, e.g. United Kingdom, and a continental country, e.g. Ukraine, as shown in Figure . While the annual data for the UK show a significant decline from  1940 to 1970, in the Ukraine the annual  

Temperature continued to rise modestly. The maritime influence is obvious. It does not support the claim that air pollution was the source. 

F34 Summery remarks

 All consideration provide a strong indication towards the role of the North Atlantic as a dominating source for the three decade long cooling period. As the correlation with naval war activities is close, the Battle of the Atlantic is a contender as a supporting source, and even a strong contender, as long as convincing reasons is not named and convincingly discussed.