"Logbooks, like the nearly 200-page document kept aboard the Eunice H. Adams, served as legal reports, necessary for insurance claims, which meant log keepers kept exhaustive records of the crew’s day-to-day exploits. They tracked the ship’s location, other vessels encountered, and both weather and sea conditions along the routes they sailed. But they also kept clues for the future: Stored within the pages of the 18th and 19th-century whaling logbooks is a cache of ancient weather records, meticulously logged by crews traversing the world’s oceans. "

https://grist.org/article/how-centuries-old-whaling-logs-are-filling-gaps-in-our-climate-knowledge/?ref=the-browser