Captain Cook’s weather logs help scientists predict climate changes

Captain James Cook’s weather reports, which he logged meticulously at noon each day on his voyages to unknown lands, are helping scientists to predict changes in the climate.

Ships’ logs from Cook’s Discovery and Resolution, William Bligh’s Bounty and 300 other 18th and 19th-century explorers’ vessels are being transcribed and digitised in a project that will allow climatologists to trace changing weather patterns.

The records, stored in the National Archives at Kew, contain a unique and highly accurate account of temperature, ice formation, air pressure and wind speed and direction in remote locations all over the world.

There are plenty of land-based weather reports from this period, but very little is known about the climate history of the three quarters of the world’s surface covered by sea.

The UK Colonial Registers and Royal Navy Logbooks project, a partnership that includes the Met Office Hadley Centre and the University of Sunderland, aims to make all the logs available online. The weather reports are being charted to allow instant comparisons between past observations and current conditions.

The log from HMS Isabella, which set out in 1818 to seek the fabled Northwest Passage, reveals that there was a small but significant decline in the sea ice in Baffin Bay over the past 190 years. Until now, scientists tracking sea ice formation have largely relied upon observations from satellites. However, some of the logs suggest that there has been little or no change in sea temperatures elsewhere in the Arctic. Climate change sceptics are likely to seize on these records as evidence that man-made greenhouse gases are having less impact than many scientists have claimed.

HMS Dorothea formed part of an 1818 Royal Navy expedition to the North Pole, commanded by David Buchan. He turned back after failing to penetrate the pack ice north of Svalbard.

The ship’s log gives the earliest account of weather in the Norwegian Arctic and shows the summer of 1818 was not markedly colder than was typical in the late 20th century.

Most of the meteorological information in the logs was taken from each ship’s barometer and thermometer, which were extremely expensive instruments at the time and were usually kept in the captain’s cabin.

Dennis Wheeler, the project leader and a climatologist at the university, said that the thermometer readings were almost always taken in the shade of the unheated cabin and were therefore directly comparable with modern readings.

The absence of marine chronometers, which were invented by John Harrison in the mid-18th century but not widely used until the 19th century, has proved fortuitous for climate scientists. Without knowing the precise time, the captains needed to log very accurate weather details, including wind speed and direction, in order to gauge their longitude. Dr Wheeler said: “Reading these logs gives me a growing respect for the navigation skills of these captains and officers. The lives of everyone on board often depended on the accuracy of their observations.

“Their conscientious and remarkably detailed reporting has given us an invaluable data resource which fills huge gaps in our knowledge about the history of the climate.”

He said that the logs helped to prove the effect on the climate of volcanic eruptions. Several captains observed a decline in temperature in 1816, which became known as the year without a summer.

The eruption of Mount Tambora in Indonesia in 1815 sent so much sunreflecting sulphur into the atmosphere that global temperatures dipped the following year, with snow reported in June in New York State.

Dr Wheeler said that the 18th-century logs were in much better condition than those from the 19th century. “The earlier logs are on very high-quality paper made from rags, while the Victorian ones are on mass-produced paper which has not survived as well.”

Victorian logs being digitised under the project include those from the Beagle, the ship that carried the young Charles Darwin on a five-year expedition around the world.

A fully searchable version of the logs will be available on the National Archives website next year.

Extracts from the logs

Captain Cook, HMS Endeavour, while surveying off New Zealand, Jan 1, 1770

“It will hardly be credited that in the midst of summer and in the latitude of 35 degrees such a gale of wind as we have had could have happened, which for its strength and continuance was such as I hardly was ever in before — fortunately at this time we were a good distance from land, otherwise it would have proved fatal to us and the ship”

Captain George McDougal, HMS Resolute, Arctic voyage, Jan 23, 1853

“The Quarter Master went outside on the floe to register the thermometers. . . In the act of reading off, his attention was attracted by a slight noise and his surprise maybe imagined when on looking round he observed a bear within five yards of him. His situation, to say the least of it, was not an enviable one, for one spring of the brute would have put an end to his registering thermometers forever. Thankfully the bear disappeared and we have the registers intact”

Captain William Parry, HMS Hecla, Winter Harbour, Melville Island, Oct 26 1819

“By a register of the temperature of the atmosphere . . . it was found that the thermometer invariably stood at least from two to five degrees Fahrenheit, and on one or two occasions, seven degrees higher on the outside of the ships than it did on the shore, owing probably to a warm atmosphere created around the former by the constant fires on board”