This post refers to my analysis of recorded annual mean temperature trends at 14 stations covering North, Central and South America. 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). 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 Americas 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:
- About 80% of the stations had a well-defined cyclical long-term trend with periods (the time between peaks in the trends) of about 80 years. Commonly trend peaks occurred around 1930 and 2010 with trend troughs around 1900 and 1960, although this does vary.
- All of the 14 stations showed evidence of a plateau or peak trend in the period since 2000.
- About 60% of the stations had a neutral (level) 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).
Nome, USA 1906-2015
Prince Albert, Canada 1884-2015
Eureka, Canada 1947-2015
Natashquan, Canada 1914-2015
Aberdeen, USA 1914-2015
Tucumcari, USA 1905-2015
Morris, USA 1886-2016
Kosciusko, USA 1889-2015
Lihue, USA 1905-2015
Faaa, Tahiti 1935-2015
Belize, Belize 1941-2015
Isla Juan Fernandez, Chile 1901-2015
Punta Arenas, Chile 1888-2015
Orcadas, Argentina 1903-2015
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. 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 Bureau of Meteorology.