Climate Change

Weather Time Machine

Old ships' logs are giving scientists new insights into the past and future of the earth's changing climate

Published December 11, 2019

In the 19th and early 20th centuries, millions of weather observations were carefully made in the logbooks of ships sailing through largely uncharted waters. Written in pen and ink, the logs recorded barometric pressure, air temperature, ice conditions and other variables. Today, volunteers from a project called Old Weather are transcribing these observations, which are fed into a huge dataset at the National Oceanic and Atmospheric Administration. This "weather time machine," as NOAA puts it, can estimate what the weather was for every day back to 1836, improving our understanding of extreme weather events and the impacts of climate change.

Why we need more data

We know a lot about weather conditions today, thanks to technologies such as satellites that deliver high-resolution imagery. Before satellites, forecasters relied on weather observations gathered with much less sophisticated instruments located around the globe. Here, one-degree squares show observations collected in January 1979.

Observations, January 19791879
Every six hours
Sea ice extent
Sept. 2019
Sept. median 1981-2010
San Francisco
North Pole
Area near Jeannette observation

But rewind a century to January 1879 and there are far fewer observations, most of them collected on land. About 70% of the Earth is covered in water and that's also where most weather happens, which makes data recorded in the ship's logs highly valuable.

A race to the North Pole

In the summer of 1879, the USS Jeannette set off on a voyage intent on making the United States the first nation to reach the North Pole — a historical equivalent of the race to the moon. The trip was funded by newspaper tycoon James Gordon Bennett Jr., who hoped the news of the Jeannette's achievement would boost circulation.

As a Navy ship, the Jeannette was run with a discipline reflected in its logbooks, which were detailed and legible. Hourly records detailed variables such as the temperature, cloud type and barometric pressure, as well as daily life on the ship.

The Jeannette quickly became trapped in the ice and spent nearly two years drifting across the Arctic Ocean. The large gap between where the Jeannette encountered the sea ice, and where that ice extends today, shows how conditions have changed in nearly a century and a half.

Going back in time

To create modern climate estimates and fold in the historic data, Dr. Kevin Wood, a climate scientist at NOAA, explained that a four-dimensional global atmospheric dataset is created by applying an algorithm using barometric pressure observations.

A supercomputer generates a grid spanning the world, from its surface to its atmosphere, allowing scientists to analyze variables such as wind and temperature across altitudes. Weather estimates are compared with observations over time, and adjusted where they differ.

A snapshot of this dataset created by Dr. Philip Brohan, a climate scientist at the Met Office in Britain, shows the weather forecast in December 1880. Gray areas represent the "fog of ignorance," or areas of uncertainty, while colored areas represent a forecast based on all available observations, including data from the Jeannette.

Date-crunching by NOAA's "weather time machine" - offically known as the third version of the NOAA-CIRES-DOE 20th Century Reanalysis, or 20CRv3 - can be used to explore trends going back further than previous climate models. While the jitteriness of the 20th-century line reflects some uncertainty, matched against other comparable models, the overlap provides greater confidence in the overall trend.

Arctic temperature anomalies

2m air temperature anomaly in Kelvins

20th Century Reanalysis V3
Japan Meteorological Agency

Before incorporating the ship log’s data, the earliest version of NOAA’s reanalysis dates to 1948, leaving out many weather events such as the 1930s Dust Bowl. The latest version allows scientists to rewind more than a century to study extreme weather patterns.

For instance, in 1880, an unusually strong storm, often called the “Sitka Hurricane,” made landfall in Alaska and is thought to be one of the strongest storms ever to strike the region. Observations from three ships, including the Jeannette, helped researchers understand that the storm was part of a much larger weather system.

'Sitka Hurricane'

Mean sea level pressure contours based on the latest 20th Century reanalysis, version 3, offers a more detailed view of the "Sitka Hurricane" due to additional observations. Credit: UK Met Office

The Jeannette's story is just one of many epic journeys into the frozen unknown of the Arctic. In 1881, a ship called the Rodgers set out from San Francisco to search for the Jeannette, adding a new set of observations to the historic weather collection.

In a sometimes-obsessive quest, hundreds of Old Weather volunteers have transcribed millions of observations from old ships' logbooks. As the Arctic ice melts away, the volunteers see their work as a rescue mission critical to understanding the state of our planet's climate.

The Bear's career spanned 89 years, two centuries, two world wars and both poles.

Read more: The climate-change secrets of 19th century ships' logs

Sources: NOAA, Old Weather, UK Met Office
Photos: REUTERS/Loren Elliott, Naval History and Heritage Command
Editing by Sarah Slobin and Kari Howard
Additional reporting by Andrew Marshall