The Stevenson Screen: Standardizing Temperature Recording

Jul 29, 2011
Sally Anne Lewis

Stevenson Screen Exterior - Alan Sim

A Stevenson Screen is a white slatted box on legs found in almost every country in the world and has been in use since 1865.

Getting a number of scientists to agree on anything has always been a problem. Especially when it comes to data collection, and even more so when the data has to be collected from different latitudes and altitudes. The Stevenson Screen was designed to hold instruments for measuring temperature, humidity and air pressure, and to avoid irregularities in data collection. Few scientists dispute its effectiveness.

Description of the Stevenson Screen

The screen is actually a box, made of a double layer of louvred screens at all four sides, with a solid top and base. The box is set on sturdy legs at a designated height, which is 1.25m in the UK, but 2m in many other places where the ground radiates a lot of heat. The whole structure is painted white to reflect the heat of the sun, and the doors open towards the north. The screen is designed to allow free passage of air, while keeping out rain and snow, leaves and animals.

The Stevenson Screen is one of a very few designs that is recommended by the World Meteorological Organization for use in every region of the world, and Stevenson Screens are also erected for use in field studies on plants or animals where temperature is part of the data collected. This widely adopted data collection device was invented in 1864 by Thomas Stevenson.

Thomas Stevenson

Thomas Stevenson was an engineer from a family of lighthouse builders. Born in 1818, his father was Robert Stevenson who built lighthouses and evidently encouraged all three sons to carry on his practice of saving ships, cargos and lives by erecting beacons to mark dangerous rocks. From his work on lighthouses, harbours and rivers, Stevenson developed a healthy respect for storms and an abiding interest in weather. He was the father of Robert Louis Stevenson who, in an article titled Thomas Stevenson – Civil Engineer, wrote: “Storms were his sworn adversaries, and it was through the study of storms that he approached that of meteorology at large. Many who knew him not otherwise, knew - perhaps have in their gardens - his louvre-boarded screen for instruments.” His interest in Meteorology led to Thomas Stevenson being one of the founders of the Scottish Meteorological Society.

The Wide Usage of the Stevenson Screen

In the British Medical Journal of May 15, 1886 the Stevenson Screen is mentioned in connection with a case of pneumonia in a region so cold that the medicine froze in the room and had to be kept under the patient’s pillow. The author of the article, Dr Wise, mentions that the outside temperature was measured within a Stevenson Screen. The screen is used in conditions varying from Saharan to Arctic, with some adaptations of size and height. Data collected in the screens is now transmitted electronically in most cases but the overall design is still the same as when Thomas Stevenson devised it in 1864.