Upminster Church stood 15 miles east of London, among a hodgepodge of farms and pastures. When William Derham ventured outside at 8 a.m. on Jan. 4, 1699, the first fingers of sunlight were still stretching over the horizon, throwing long shadows behind the church’s bell tower and trees. A breeze blew from the southwest, and clouds crept over the sky. Derham ducked into the cool shade to examine an object that hung there. The local Anglican rector, Derham was better known for his observations of Jupiter and his collections of wasps and grubs than for his talents in the pulpit.
On this day, he had come to take the first reading from his thermometer, still a new technology at the time. Derham’s was custom-built: a 2-foot shaft of glass with a bulb at the bottom filled with alcohol. The Fahrenheit and Celsius scales weren’t yet invented, so he read the temperature on his instrument using his own system: 1 degree for every tenth of an inch. When Derham read the thermometer that winter morning, it was mild — 11.00 inches of alcohol, or 110 degrees — roughly 48 degrees Fahrenheit. He would continue reading the temperature thrice daily for the next seven years, recording it along with the wind, rain, barometric pressure and clouds.
Derham could not have known, but his hobby would one day mark the beginning of something monumental: the Central England temperature record, the earliest thermometer readings now included in the massive datasets that track global warming. Eventually, scientists would use Derham’s readings — among others — to better understand human-caused climate change.
Records Store The vast majority of the world’s temperature readings don’t go back further than the 1900s, when large-scale burning of fossil fuels was already underway, and with it the release of planet-warming greenhouse gases. Such a short record makes it difficult to measure natural variations in climate that existed before humans began warming the world; as a result, it complicates efforts to tease apart how much of the planet’s warming has been caused by humans versus natural factors.
