Logbooks from the eighteenth and early nineteenth century had previously been used in case studies of individual events of historic or climatic interest.
CLIWOC established early ships' logbooks as another source for those seeking to understand climate change, to be used alongside proxy and instrument data.
The range of information - wind force terms and directions, and general weather descriptions - is consistent between the different national sources.
The vocabulary used also differed between the national sources - British mariners used a relatively narrow range of terms, while sailors from the Netherlands, Spain, and France used a wider set of descriptions.
[1] In order to establish the reliability of logbook records, the researchers looked at readings taken where ships were in convoy or travelling in close company.
Precise navigational methods were not widely used until late in the study period, so it was necessary to correct latitude and longitude using specifically designed software.
The database was used to feed wind force and direction into statistical models, which in turn produced monthly pressure field reconstructions for the Indian and the South and North Atlantic Oceans.