There is only a slight difference between the Northern and the Southern Hemisphere, but is this apparent agreement real? Only 31.4% of the Southern Hemisphere had acceptable measurements.
The most comprehensive series of measurements were those made in the Atlantic Ocean. Here there was a marked positive temperature change gradient between the north and the south; from -0.11°C for the North Atlantic, to 0.64°C for the north east Atlantic, to 0.44°C for the Middle Atlantic, 0.75°C for the South East Atlantic and 0.84°C for the South East Atlantic. There is a similar positive gradient between the Arabian Sea/ Bay of Bengal (0.53°C) and the sea route Capetown to Australia (0.91°C)
If the results from these oceans are combined with comparisons between land measurements in Western Europe (0.50°C) and the USA (0.40°C), in the Northern Hemisphere, and with South Africa (0.76°C), Eastern Australia (0.64°C) and Chile/Argentina (0.67°C) in the Southern Hemisphere, a case can be made for a greater temperature increase in the Southern Hemisphere than in the Northern Hemisphere.
This change is, however, counteracted by the very large positive temperature change in the former Imperial Russia/ Soviet Union. Russia/Western Siberia was 1.19°C and Eastern Siberia 1.30°C.. The conclusions from the overall figures that there was little or no difference between the temperature changes of the Northern and Southern Hemispheres between 1901 and 1996, and that the mean temperature change in the Northern Hemisphere over that period was 0.58°C, are heavily dependent on the Russian results.
It is unfortunate that measurements in the Pacific Ocean are so sparse. The mean temperature change in the North Pacific was high, at +0.90°C . The sea route from North America to Auckland had a mean temperature change figure of + 0.65°C, and there was a marked fall in the temperature change from North to South. Several of the sparse measurements near the centre of the ocean were negative. It looks as if there may have been a fall in temperature change from north to south , but with so much of the area not measured, this conclusion must be tentative.
Falls in temperature were recorded in the North Atlantic (-0.11°C), Alaska/Yukon (-0.12°C), South Greenland (-0.44°C), SW China/ Tibet (-0.44°C), SW United States (-0.37°C), Bolivia (-0.46), Nigeria (-0.43°C) and in Madagascar (Tananarive) (-0.61°C). The last two need to be questioned. The five low points in Nigeria are next to a neighbouring point of +1.46°C in Timbuktu. Madagascar is surrounded by sea with a temperature rise of +0.64°C. Also, there were no records for Tananarive between 1916 and 1931. The most extreme example in Karl’s dataset is the stated mean annual temperature anomaly for 77.5N. 12.5E (Spitzbergen) for the year 1917 of -7.63°C, when only 1500 km away in the Greenland Sea, the value was -0.03°C.
The data do not cover major regions of the globe. These include almost all of the Pacific Ocean, the Southern Ocean, the South Indian Ocean and South China Sea, most of Africa, Brazil, Central Siberia, the Arctic and Western Australia. The results for the Southern Hemisphere are particularly sparse. If it turned out that there was some doubt over the Russian/Soviet figures, then a positive temperature trend between the Northern and Southern Hemisphere, as shown by the Atlantic Ocean, could exist, as predicted by the cooling effects of sulphate aerosols, which should be greater in the Northern Hemisphere.
The fact that many of the data are missing from the 1914-1918 and 1939-1945 periods, raises doubts about the continuity of data in many 5°x5° grids, where measurement sites would probably have changed personnel, location and instrumentation over the period.
The limitations of Karl’s dataset would appear to apply also to the widely accepted surface temperature record from which it was derived (i.e. Jones 1994, Parker and Folland 1995)
More detailed subdivision of Karl’s (1998) data into smaller regions indicates that there is much greater regional variability in temperature change than has been previously recognised. This casts doubt on the representativeness of surface temperature measurements made in, or derived from only one or a few places.
Karl’s (1998) data suffer from a number of limitations which affect these conclusions, as well as those of his own study. Since these limitations must also be associated with the basic data used to establish the surface temperature record, established by Jones (1994) and Folland and Parker (1995), then that record has to be questioned also.
The evident local heating in rural sites in cold regions shows that assumptions about the absence of “urbanisation” are incorrect. Local heating effects undoubtedly occur in both urban and rural sites, and they go far to explain the discrepancies between the surface temperature record and that of the lower troposphere, as measured by satellites. This represents a major part of the supposed “ human” influence on the climate.
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