This post refers to my analysis of recorded annual mean temperature trends at 7 stations located in large cities in “other” regions of the world, excluding Europe, USA and Asia. The stations were all with long records (all over 95 years) and located in large cities (mostly with populations over a million). 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.
Normally data from stations located in cities are not suitable for general studies of climate trends (except within urban areas!), because of the uncertain effects of urbanisation on the temperatures. However, city data are often longer than rural data, and it is interesting to compare their long-term trends. It is generally considered that urban temperatures have risen considerably during the past half-century due to increased development (roads, buildings, airports, etc) and increased air pollution (due to industrialisation and vehicles). The urbanisation effect may vary considerably in different cities; for example, if a station is located near a coast there may be minimal urbanisation effect. Another uncertainty with urban stations is that their locations may have changed over the years. Also, prior to the introduction of Stevenson screens in the late 19th century, the instrumentation was different and this will also affect the apparent long-term temperature trends.
This selection of 7 “Other” cities is part of a larger analysis involving 50 cities, worldwide.
Plots are shown below for the 7 “Other” 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).