Temperature measurement and the Stevenson screen
To measure the temperature of the air accurately, it is important that the thermometer is shielded from direct sunlight but is still exposed to a good airflow. The standard screen used internationally to shelter instruments is a double-louvred wooden box, with the instruments 1.2 to 2.0 metres above ground level. This screen, known as 'a Stevenson screen', was designed by Thomas Stevenson (1818-1887), a British civil engineer and father of Robert Louis Stevenson. The use of a standard screen allows temperatures to be compared accurately with those measured in earlier years and at different places.
The Stevenson screen was first introduced to Australia in the 1880s and was installed everywhere, with a few exceptions, by 1910. Prior to this date, thermometers were located in various types of shelter, as well as under verandas and even in unheated rooms indoors. Because of this lack of standardisation, many pre-1910 temperatures in Australia are not strictly comparable with those measured after that date, and therefore must be used with care in analyses of climate change within Australia.
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