Published data were used to analyse the long-term annual temperature trends at five locations located in northern Africa. Stations selected were located in Algeria, Mali and Sudan.
The data used were all from the website of KNMI (the Royal Netherlands Meteorological Institute). Only raw data were used (ie as originally recorded, without any adjustments). Data were only used from stations located in rural areas or in small towns so as to avoid the possible influence of urbanisation on the temperatures.
The periods of the data ranged from 47 years to 116 years of complete annual data. The earliest record, at Dar el Beida, commenced in 1856.
The plots shown below are of the annual mean temperatures at each of the five locations. On each plot a polynomial “best fit” trendline has been added. It should be noted that the trendlines near each extremity (ie near the start and end of the records) are quite sensitive to individual data points, whereas trendlines within the main body of the record are much more stable and reliable.
COMPARISON OF TRENDLINES
Annual Mean Temperature Trends
[ The basis of these trendlines can be seen from the analyses for the five individual stations – see next section. To avoid congestion and a condensed scale the trendlines are also shown on three separate plots. ]
Annual Mean Temperature Residual Trends
[ The individual trend-lines have been adjusted by constant amounts to be approximately zero at the trend-lines around 1970.
ANNUAL MEAN TEMPERATURE TRENDS FOR INDIVIDUAL STATIONS
Dar el Beida (Algeria ) 1856-2015
Tombouctou (Mali) 1898-2003
Kayes (Mali) 1896-1990
Wadi Halfa (Sudan) 1904-2010
El Obeid (Sudan) 1909-2012
DISCUSSION AND COMMENTS
- The data analysed was limited to that which were available on the KNMI website.
- The annual mean temperature trend-lines for five stations located in Algeria, Mali and Sudan showed cyclical patterns, but with different characteristics. The two stations in Mali showed decreasing trend-lines prior to around 1980, while the other three stations showed increasing trend-lines over the same period.
- Excluding El Obeid, the other four stationsshowed increasing trend-lines since around 1980-1990.
- The increase in temperature from ~1970 to ~2000 was generally 0.5-1.0 deg C.
- The trend-lines of the five stations varied considerably.
- Four of the five stations showed increasing trend-lines since around 1980-1990.
- El Obeid was an exception having a cyclical trend-line but a High around 1990.
This article was written by Brian Gunter of Narooma, NSW. In his previous life Brian was an engineering hydrologist involved over many years in the analysis of rainfall and river flow data for the planning of water resources projects in Australia, Asia and Africa. In recent years he has been one of the Marine Rescue NSW (previously Royal Volunteer Coastal Patrol) volunteer weather observers who operate the Narooma station for the Bureau of Meteorology.