This post refers to my analysis of recorded monthly mean temperature trends at Pietersburg in northern South Africa. The station was established in 1932. The analysis used raw data (as recorded, without any adjustments) as published by KNMI (the Dutch Meteorological Institute). Polynomial curves of best fit were added to the plots.
Pietersburg, a city with a population of 130,000, was renamed Polokwane in 2005. Pietersburg is located at an elevation of 1,230 m.
Over the 1932-2016 period (a period of 84 years) the years are 94% complete.
Pietersburg has an semi-arid climate with cool winters and mild summers. Mean monthly temperatures vary from 11.9 degC (in July) to 21.9 degC (in January). Extreme monthly mean temperatures recorded are 9.5 degC (in June 1935) to 24.9 degC (in February 1992).
Mean, Maximum and Minimum Monthly Temperatures
Plots are shown below for annual mean temperature and the monthly mean temperature for each of the 12 months. A polynomial trendline was fitted to each graph. A comparison of the monthy trendlines are also presented. It should be noted that the trendlines (in red) can sometimes be misleading at either end of the series as the line is very dependent on the temperature values in individual years (this sensitivity does not occur away from the start and end of the series).
Annual Mean Temperatures
Monthly Mean Temperature Trendlines
- The plots show slight cyclical monthly trendlines in most months, with Highs in about 1960 and 2010 and a Low in about 1980.
- A plateau in the trendline around 2000/2010 is observed to occur in most months.
- The average annual temperature trend since 1932 is about +1.8 degC/century.
- There are no alarming increases in the temperature trendlines in recent decades.
Pietersburg is one of 257 stations, worldwide, for which I have analysed long-term temperature trends. The analyses at 50 representative stations are summarised in the blog post: world-50-temperatures
Please let me know what you think of my analyses. firstname.lastname@example.org
This article was written by Brian Gunter of Narooma, NSW, Australia. 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 Australian Bureau of Meteorology.