91涩漫

Researchers have uncovered and digitized nearly two million 18^th and 19^th century weather observations from across Canada that offer new insights into how the country鈥檚 climate has changed over time.

The international project draws on handwritten records dating from 1768 to 1884. The data include temperature, precipitation, wind and detailed descriptions of such events as storms and floods.

鈥淭he paper is a data study, so in that sense we were looking for, documenting and transcribing meteorological observations from overseas archives, given Canada鈥檚 colonial history,鈥� said Victoria Slonosky, an afiiliated researcher in the Department of Geography and lead author of .

To build the dataset, researchers obtained fragile documents digitized by archives, transcribed the observations into a database and converted the measurements into modern units. Slonosky also helped establish , a not-for-profit organization that supports the search and transcription of Canadian weather records, along with related efforts such as 91涩漫鈥檚 .

Researchers drew on military and medical weather logs held in the United Kingdom鈥檚 Meteorological Office archives and records at the U.S. National Archives, including observations by Hudson鈥檚 Bay Company employees and missionaries.

Rich detail from the past

One surprise was the level of detail: Observers often recorded conditions two or three times a day and noted far more than temperature.

鈥淎s well as thermometer observations, there are wind, cloud, rain, snow, atmospheric humidity and atmospheric pressure observations, along with descriptions of the weather and sky,鈥� Slonosky said.

These accounts include descriptions of floods, fires, storms and aurora, allowing researchers to identify past extreme events.

Filling a major knowledge gap

Until now, much of Canada鈥檚 early weather record was poorly understood, especially pertaining to northern and western regions.

鈥淭here was a 鈥榝og of ignorance鈥� 鈥� for this area,鈥� Slonosky said, noting that limited data has made it harder to understand how storms form and evolve over time.

The newly digitized records suggest the climate in this period, near the end of the Little Ice Age, was highly variable.

鈥淲e knew it was generally colder than today, but discovering such a wealth of information also helps us see that the weather was more variable than in the 20th century generally,鈥� she said.

Understanding how disruptive weather events happen

Researchers say the findings will help improve understanding of extreme weather events that affect people now and may also help put today鈥檚 climate headlines in context.

鈥淲e see the word 鈥榰nprecedented鈥� a lot 鈥� so we鈥檇 like to find out if some of these things really are unprecedented, or if we just have short records and shorter memories,鈥� Slonosky said.

About the study

by Victoria Slonosky et al. was published in Nature鈥檚 Scientific Data. It was funded by Environment and Climate Change Canada.