How 18th- and 19th-Century Whaling Logbooks Are Improving Modern Weather and Climate Research

Boaters and meteorologists alike rely on instruments, satellites, and complex models to predict weather, but there’s growing recognition that valuable historical observations are hidden in an unexpected place: handwritten whaling ship logbooks from the late 18th and 19th centuries. These journals, kept by crews who sailed into remote ocean regions long before modern observation networks existed, are now being mined for climate and weather data to help extend and improve modern forecasts and climate models.

A collaborative project led by Timothy Walker, a history professor at the University of Massachusetts Dartmouth, and Caroline Ummenhofer, a climate scientist at the Woods Hole Oceanographic Institution (WHOI), is transcribing thousands of these logbooks and converting their entries into digital data. Their team is extracting day-by-day records of wind, sea state, and other observations recorded by whalers who regularly ventured far beyond the usual shipping lanes into parts of the ocean that remain sparsely documented.

“Whalers sailed to very remote ocean areas 250 years ago, where we have almost no direct information about past weather and conditions,” Ummenhofer explains. “Some of those regions are now experiencing substantial changes in wind patterns, and these records provide a rare long-term perspective.”

The project began when Walker, while crewing on the historic schooner Ernestina-Morrissey in New Bedford, discussed archival weather data with oceanography colleagues and learned about citizen-science efforts such as the Old Weather project. He realized New Bedford already houses one of the world’s largest collections of whaling logbooks—about 3,000 items combined between the New Bedford Whaling Museum and the New Bedford Free Public Library—and contacted Ummenhofer to explore converting those handwritten records into usable climate data.

Ummenhofer’s research examines the ocean’s role in climate variability and extreme weather, including how ocean conditions influence rainfall and storm behavior. To answer questions about why one year is unusually dry while another is wet, or to better understand shifting wind patterns, researchers need observational data that extend much farther back than modern instrumental records and cover remote ocean regions. Whaling logbooks can fill that gap because whalers recorded conditions in locations rarely visited by other vessels.

These logbooks often contain detailed day-to-day notes about wind direction, wind strength, and the sea state—information that climate modelers value highly. “They were paying close attention to wind direction, wind force, and sea conditions,” Walker says. “That observational detail is extremely useful for improving historical weather reconstructions.”

Working with these archives presents several challenges. Fortunately, most logbooks are well preserved on durable cotton rag paper and stored in controlled archival conditions. The greater difficulty is that every logbook is unique: entries vary in format, length, and handwriting. A single page might cover four days or twenty-five days, and the handwriting styles—often cursive—change from one logkeeper to another. Those variations make automated optical character recognition unreliable, so human readers are essential.

Deciphering the nautical vocabulary in the entries is another hurdle. Whalers did not have modern anemometers to record precise wind speeds, so they used descriptive terms such as “fresh breeze,” “strong day,” or “storm.” The research team translates those historical expressions into modern meteorological equivalents using prior work that correlates such phrases with the Beaufort Wind Scale. For example, a “gentle breeze” usually maps to Beaufort Force 3, a “strong breeze” to Force 6, and a “storm” to Force 10. These translations let climatologists convert qualitative notes into quantitative datasets.

“Not all terms are used equally, and many different expressions can correspond to the same Beaufort force,” Ummenhofer notes. “We also see fewer mentions of the very strongest forces, which could reflect survivorship bias—ships encountering the most extreme storms may not have returned to record them.”

After volunteers and researchers transcribe the entries, the data are entered into a project database and undergo quality control at WHOI. That process includes validating locations, assigning coordinates, and ensuring consistency across entries. Since 2017, the team has reviewed about 110 logbooks and extracted roughly 60,000 individual entries, of which about 32,000 are judged usable for climate analysis.

Walker emphasizes the human side of the archives as well: “You find personal stories—desertions, fights, difficult voyages—while you’re transcribing. But our priority is the weather data these records contain.”

With the concept proven, the project aims to scale up. Five New England institutions—the New Bedford Whaling Museum and the New Bedford Free Public Library plus the Providence Public Library, the Nantucket Historical Association, and Mystic Seaport Museum—hold the vast majority of U.S. whaling logbooks, estimated at roughly 85–90 percent of known collections. Together these repositories contain about 5,500 logbooks that could be studied, depending on funding and staffing.

“The potential impact is significant,” Ummenhofer says. “The more historical data we can bring into climate models, the better our reconstructions of past ocean and atmospheric conditions will be. Building the dataset is the hard part; we’ve started, and now broader support and funding will help expand the effort.”

Kim Kavin

This article was originally published in the February 2023 issue.