This post refers to my analysis of recorded monthly mean temperature trends at Cape Leeuwin in southwestern Australia. The station was established in 1897. The analysis used raw data (as recorded, without any adjustments) as published by BOM (the Australian Bureau of Meteorology). Polynomial curves of best fit were added to the plots.
Cape Leeuwin is located in a National Park near a lighthouse, located on a promontory in the south-west of Western Australia. The station is directly exposed to the Indian Ocean.
Over the 1897-2016 period (a period of 120 years) the years are 100% complete.
Cape Leeuwin has a humid Mediterranean climate, with mild winters and warm summers. Mean monthly temperatures vary from 13.9 degC (in July and August) to 20.3 degC (in February). Extreme monthly mean temperatures recorded are 12.2 degC (in August 1951) to 22.5 degC (in February 2011).
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 variable cyclical monthly trendlines, with Highs in about 1910 and 2010 and a Low in about 1940.
- The monthly mean temperatures around 2000-2010 are between zero and 1 degC higher than in around 1910.
- In most months there is a peak or plateau in the temperature trends around 2000-2010.
- There have been no alarming trends in temperatures in recent decades.
Cape Leeuwin 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.