This post refers to my analysis of recorded annual mean temperature trends at 14 stations extending from southern Africa to Austalia, New Zealand and Antarctica. The stations were all with long records (many over 100 years) and located in rural areas or small towns. The analysis used raw data (as recorded, without any adjustments) as published by KNMI (the Dutch Meteorological Institute or BOM (the Australian Bureau of Meteorology). Polynomial curves of best fit were added to the plots.
In all, a total of 257 stations worldwide were used in a larger analysis, but these have been summarised here by selecting 14 stations in the Southern Africa-Australia-New Zealand region. The selected stations were not “cherry-picked”. Links to separate summaries in three other regions, with a total of 36 stations, are given below. Links to the analyses at the 257 individual stations (worldwide) are also given below.
No attempt was been made to derive “regional average” temperature trends. Instead analyses were made at individual stations as this was considered to be more physically meaningful and practical using thermometer observation data. Using this approach any inconsistencies due to data quality would be identified as outliers.
The analyses at these 14 stations showed that:
- Only about 20% of the stations had a well-defined cyclical long-term trend with periods (the time between peaks in the trends). Commonly trend troughs occurred around 1940-1970 with trend peaks around 2010, although this does vary considerably.
- About 90% of the stations showed a plateau or peak trend in the period since 2000.
- At about 10% of the stations there no evidence of a peak in the trend since 2000.
- About 40% of the stations had a neutral or negative overall trend over the past century.
Plots are shown below for the 14 stations. It should be noted that the polynomial fit line (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).
St Helena, UK 1892-2015
Pietersburg, South Africa 1932-2015
St Brandon, Mauritius 1951-2015
Cape Leeuwin, Australia 1897-2016
Marble Bar, Australia 1901-2016
Darwin, Australia 1882-2016
Richmond, Australia 1893-2016
Moruya Heads, Australia 1910-2016
Lord Howe Island, Australia 1912-2016
Hokitika, New Zealand 1866-2015
Macquarie Island, Australia 1948-2016
Mawson, Australia 1954-2016
Halley, UK 1956-2015
Amundsen-Scott, USA 1957-2015
For convenience of management the 50 selected regional stations have been grouped into four large regions (see map below) as follows:
- Americas region, 14 stations
- Europe and northern Africa region, 9 stations
- Asia region, 13 stations
- Southern Africa, Australia, Antarctica region, 14 stations
Links to the analyses of the long-term temperature trends at the other 36 stations are presented within the other three large regional blog posts:
The analyses at the 50 worldwide stations are summarised in the blog post:
Similar links the the analyses of the long-term temperature trends at all 257 stations analysed are presented within 27 smaller regional blog posts:
- southern africa-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 Bureau of Meteorology.