By Ed Caryl
In A Recent Temperature History, Part 1, the temperature trends for the contiguous United States were examined. In part 2, the rest of the world (as far as there is data) will be explored. Again, the selection criteria were: less than 10,000 population, and (as much as possible) a continuous record from 1940 or before to the present.
Ten stations were found in the Arctic and Siberia, six stations bordering the North Atlantic Ocean, and thirteen stations in the southern hemisphere, in South American, Australia, the south Atlantic, and south Pacific. All of these stations are well away from any population centers and are isolated or in or associated with very small towns and villages. No stations were found in continental Europe or Africa that met the above criteria. Station records at GISS either ceased in 1990, had a large gap during WWII, or both.
Figure 1. These are Arctic and Siberian temperature anomalies using 1930 to 1980 as the baseline period. The bold black trace is the average of these ten anomalies.
In the Arctic and Siberia we see the familiar pattern of warming in the first half of the 20th century, followed by cooling until 1970, then warming until recently.
Figure 2: The Arctic and Siberia average anomaly and a linear trend line from 1930 to the present. The trend is +0.33° C over the 80 years, or about 0.4° C per century.
The problem with the trend in Figure 2 is that it includes part of the earlier warming trend and only one cooling period. In Figure 3, the 66-year complete cycle is chosen, and there is no trend.
Figure 3. The Arctic and Siberian trend over the period 1943 to 2000.
The North Atlantic shows the same shape as the other Northern Hemisphere records.
Figure 4. There are six North Atlantic temperature anomalies. The bold black trace is the average of the six stations. Before 1900, only the Akureyi station on Iceland was active.
Figure 5. This is the North Atlantic average anomaly and the linear trend from 1930 to the present. The trend from the mid 1930’s to the present is flat.
In the northern hemisphere the temperature trend is a cycle, roughly paralleling the Atlantic Multi-decadal Oscillation (AMO), and the Pacific Decadal Oscillation (PDO). Between the cycles of that oscillation, there is no trend. There may have been a trend in the 19th century of warming from the LIA, but that is now over.
The Southern Hemisphere
There are few stations in the Southern Hemisphere that meet the criteria for admission into this exclusive club. South Africa has none. Australia has three, two at airports, but not large airports. South America has four stations, the rest are on islands in the Pacific, and there is one in the South Atlantic. There were no stations in Antarctica before 1955. Most stations in Antarctica were established during the International Geophysical Year from July 1, 1957, to December 31, 1958. Still, there are five stations in the southern hemisphere that go back to the turn of the 20th century.
Figure 6. There are 13 Southern Hemisphere stations with long records. The baseline for these anomalies is, again, 1930 to 1980. The bold trace is the average anomaly.
In Figure 6, the Argentine Base Orcada on the South Orkney Islands in the South Atlantic provides much of the noise.
Figure 7: This is the Southern Hemisphere average anomaly with the linear trend line.
The notable thing about the southern hemisphere trend is that there isn’t any trend. The eye tries to detect a pattern of cooling early and a slight warming since 1930, but it would be about 0.1° C. If real, this may be half of the 200-year cycle discussed in the Lui et al paper, and here. But it might be urban warming creeping into the data. Some of the positive peaks coincide with major El Nino years, particularly 1891, 1982-83, 1997-98, and 2010. Over the last 50 years, continental Antarctica itself seems to be cooling slightly. See A Wind in Antarctica.
In the beginning, the exercise described in this two-part article was an attempt to tease out an accurate measure of global warming in order to determine CO2 sensitivity, the amount of warming we would experience if CO2 were to double. During the 20th century, CO2 in the atmosphere has increased from about 280 parts per million (ppm) to 390 ppm. This is about 40% of doubling. If doubling the CO2 in the atmosphere were to cause appreciable warming, we should see a measurable amount now. The climate sensitivity can be calculated from that amount. That number has now been found.