This post refers to my analysis of recorded monthly mean temperature trends at the small city of Ishigakijima in the far south of Japan. The station was established in 1897. 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.
The Ishigakijima station is located on Ishigaki Island in the far south of Japan, 260 km east of Taiwan.
Over the 1897-2016 period (a period of 120 years) the years are 97% complete.
Ishigakijima has an sub-tropical climate with mild winters and hot summers. Mean monthly temperatures vary from 18.1 degC (in January) to 28.9 degC (in July). Extreme monthly mean temperatures recorded are 13.3 degC (in February 1901) to 30.8 degC (in July 1956).
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, but there has been a consistent increase in temperature over the past 120 years.
- A plateau in the trendline around 2000/2010 is observed to occur in most months.
- The average annual temperature trend since 1897 is about +1.3 degC/century.
- There are no alarming increases in the temperature trendlines in recent decades.
Ishigakijima 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. email@example.com
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.