ROPEWALK: Turning Historical Weather Logs into Climate Data

ROPEWALK (“Rescuing Old data with People’s Efforts: Weather and climate Archives from LogbooK records”) is digitizing weather observations from sea voyages dating back to the 16th-18th centuries. These records come from logbooks meticulously kept by Danish ship captains and officers during their global expeditions.

This project transforms these historical accounts into unique datasets for contemporary climate models. There’s no comparable source of weather data from that era, making these never-before-used observations invaluable for understanding past weather patterns and predicting future climate changes.

The project is a joint venture between the Danish National Archives and the Danish Meteorological Institute. It’s been made possible thanks to a generous 14.25 million kroner grant from the A.P. Møller and Chastine Mc-Kinney Møller Foundation. ROPEWALK kicked off in early 2023 and is set to continue until 2027.

The National Archives houses an impressive collection of maritime documents – over 700 shelf meters of ship journals, logbooks, and other nautical records from thousands of Danish vessels. Some of these documents date all the way back to 1675.

While a significant portion comes from the naval fleet, there are also substantial collections from the Royal Greenland Trade Department and the Royal Danish Academy of Sciences and Letters. These authentic, handwritten observations are now being transformed into quantitative climate data, ready to fuel new research.

Danish ship captains were required to maintain detailed logbooks and journals during their voyages, recording all significant events on board – including weather conditions. These meticulous records provide valuable insights into wind patterns, ocean currents, seasonal ice formations, temperatures, and atmospheric pressure.

Using advanced analysis techniques, each individual observation can be geolocated and precisely mapped. This allows researchers to reconstruct historical weather patterns and understand local climate conditions of the past, but they can also use this data to predict climate development.

In the spirit of open science, all Danish ship journals will be made freely accessible to not only Danish and international climate researchers but also to anyone with an interest in maritime history or life aboard Danish ships during their global voyages.

If you’re intrigued by the project and want to stay updated on its progress or have any questions, please contact ropewalk@rigsarkivet.dk.