This post refers to my analysis of recorded annual mean temperature trends at 15 stations located in large cities in Asia. The stations were all with long records (all over 100 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 15 Asian cities is part of a larger analysis involving 50 cities, worldwide.
Plots are shown below for the 15 Asian 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).
[ The Yerevan temperature trend was essentially constant between around 1930 and 2000. The present-day temperatures are about 1.0 degC higher. ]
[ The Omsk temperature trend was essentially constant between around 1920 and 1960. There was an increase of about 1.5 degC between 1960 and 1995, but the temperatures have been essentially constant since then. ]
[ The Almaty temperature trend has a cyclical pattern with Highs around 1930 and 2010(?). The temperature trend was essentially constant between around 1920 and 1970. There was an increase of about 1.5 degC between 1970 and 2000, but the temperatures have been essentially constant since then. ]
[ The Tashkent temperature trend was essentially constant from the 188s until around 1950, but have increased steadily by about 2.0 degC since then. ]
[ The Lahore temperature trend is cyclical with Highs around 1890, 1940 & 2010(?) and Lows around 1910 & 1970. The present-day temperatures are about 0.5 degC higher than around 1940. ]
[ Bombay temperatures rose steadily by about 1.2 degC between 1878 and 1930. The temperatures were then essentially constant until around 1970, after which they have increased by about 0.5 degC. ]
[ The Calcutta temperatures between 1830 and 1850 are about 2.5 degC higher than the general trend and therefore are probably inconsistent. Between around 1880 and 1950 the temperature rose steadily by about 1.0 degC. Between 1950 and 1990 the temperarures were essentially constant, but they have since risen by about 0.4 degC. ]
[ The Madras temperatures were essentially constant between around 1840 and 1950. They have since increased by about 0.7 degC. ]
[ The Colombo temperature trend is cyclical with Highs around 1890 & 2010(?) and a Low around 1940. ]
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 Meteor