WHAT do you see out of your window? Many people have reported during lockdown that they are noticing nature and the weather more. Lockdown has undoubtedly led to cleaner air due to reduced pollution, and more wildlife due to fewer people outside, but it seems likely that many people simply have more of an opportunity to notice things. The weather is one of them: not for nothing did the poet Ralph Waldo Emerson call the sky “the daily bread of the eyes.”

Of course, some will have been keen observers of the weather pre-lockdown. One of the Science and Society team’s grandmothers has been keeping a weather diary every day for several decades, inspiring in her grandchildren an interest in the observation of nature.

Such practices date back a long way. The earliest known weather diary in Europe was made by William Merle, a 12th-century parish priest in Driby, Lincolnshire, who recorded the weather between 1337-1344. No previous document exists with comparable detail.

As Alexandra Harris notes in Weatherland, her survey of English weather writing, Merle’s record of the weather “stands apart from its time.” Example entries include for September 1339: “the first, second and third weeks were rainy, and the fourth more rainy than the preceding weeks.” Merle may have continued past 1344, but his records stop then (perhaps he got disheartened by all the rain). 

It was not until centuries later that professional weather organisations were set up. With the invention of reliable sealed thermometers unaffected by atmospheric pressure, the wealthy Ferdinando II de’Medici decided to fund the collection of temperature data from across Europe.

Ferdinando and the other Medicis were closely linked to new technological methods due to their important status as wealthy patrons. Galileo Galilei originally named the four moons of Jupiter he was able to observe with his telescope the “Medicea Sidera” (Medician stars) in their honour. Later, in 1632, Galileo dedicated his Dialogue to the “Gran Duca,” a work that would see him accused and convicted of heresy by the Catholic Church.

Ferdinando’s weather observation network commenced in 1654, and is generally acknowledged to be the first historical temperature series. As a 2012 paper in the journal Climatic Change sets out, the network was set up to try to provide directly comparable data between different locations to test theories about how winds from the north and south affected temperature.

In 1654, identical thermometers were sent to monks in eleven locations, mostly within northern Italy but including Innsbruck, Warsaw, and Paris, with precise instructions about where to hang the thermometers and how often to take measurements.

Monks were chosen as they could be trusted to keep a strict schedule: the monks had to record between five and eight observations a day, including night-time observations. As the authors of the paper note, the thermometers were probably kept at locations within the walled monastic communities because of the risk from “wild animals and bandits” if taking observations outside at night.

The network was closed down in 1667, ostensibly because of increasing concern about the way it was linked to Galileo’s ideas which privileged “instrumental observations” over the Bible. However, many of the monks’ records survive, and can be analysed with modern methods to give us a unique window into the climate of the time.

If you noticed that it seemed unusually sunny last month, you’d be right: it was the sunniest May “on record” in Britain. As Professor Joe Smith commented to the BBC, such observations of unexpected weather are “a signal of the increasing unpredictability” of our climate. However, Met Office records only date back to the 19th century.

For more distant times, other historical sources can still be used. The effect of climate on history was recognised by the French historian Emmanuel Le Roy Ladurie in a far-sighted article Histoire et Climat in 1959. Changing climatic conditions often produce changing economic conditions, and thus have important effects in social history.

Le Roy Ladurie and others have shown the value of unexpected historical documents for such climate research. For example, grape harvests from French vineyards are strongly correlated with temperature records from the 19th century, suggesting that harvest documents from previous centuries can be used as reliable temperature records.

Unorthodox weather records continue today. The Met Office Weather Observations Website (WOW) collects “amateur” weather observations. As researchers writing about such observations make clear, the term “amateur” refers only to those who record the weather due to passion or personal interest rather than because it is their job.

Set up in 2011, looking at the WOW is a heartwarming experience, thanks to the many hobbyists who submit whatever they like to be archived by the Met. Many amateur observers are in fact self-taught experts.

Steven Jay Gould once wrote about “the large number of common activities requiring a good deal of scientific understanding, but not usually so classified.” Weather observations are one of these. Noticing the weather, comparing it to previous days, recognising its notable features and recording them, is a quintessentially scientific approach.

It may seem pointless to write down your own observations of the weather, when professional institutions hold vast data reserves and the information travels round the world in seconds — but the experience of observers adds value to records. Despite our present-focused world, all it takes to transform the mundane into the historical is time.

Those who take the simple act of writing down what’s happening outside their window turn their transitory experience of weather into a historical record. A common saying in statistics is “the plural of anecdote is not data.” We couldn’t disagree more.