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'Since records began': a brief guide to who's taking the temperature

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Richard Cable | 19:35 UK time, Monday, 30 March 2009

Stories about climate change are frequently accompanied by the phrase 'since records began'. The 10 hottest years since records began have apparently all happened since 1997. But whose records and when did they begin?

The oldest ongoing instrumental record of temperature in the world is the Central England Temperature record, started in 1659. But it wasn't until the mid-19th century that we started to take the temperature 'globally', and not until 1873 and the foundation of the International Meteorological Organisation that we all started to try and take the temperature in the same way.

By global temperature, at this time we mean predominantly Europe, bits of the then-British Empire (India, Australia, South Africa) and North America. It's probably fair to say that 'true' global coverage of readings in meaningful densities around the entire planet didn't arrive until post-World War Two. (See diagram.)

This map shows the 7,280 fixed-temperature stations in the Global Historical Climatology Network catalogue, colour-coded by the length of the available record. (Created for Global Warming Art by Robert A Rohde.)


To this day, we still rely on a basic network of weather stations on land (many are still 'Stevenson screens' - those things that look like beehives on sticks) and ships at sea. But the sophistication and ambition of climate monitoring has literally sky-rocketed in the last 20 years, not least with the European Space Agency's Earth Explorers programme.

So there you have it. When someone says 'since records began', they probably mean 'since about 1880'.


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