The principal objective of the CLIWOC project was to realise the scientific potential of logbook climatic data and to produce a database of daily weather observations for the world's oceans between 1750 and 1850. Another objective was to provide a comprehensive understanding of the nature of climatic change over the oceans for the century after 1750 when logbooks became abundant and to link with existing databases such as the I-COADS dataset (International Comprehensive Ocean-Atmosphere Data Set). The study period is also significant because it marks a period when climatic change cannot be seen as a consequence of world-wide industrialization and the release of greenhouse gases into the atmosphere. One of the project's main achievements was the preparation of a database drawing on British, Dutch, French and Spanish naval logbook records for the immediate pre-instrumental period (1750-1853). This database is freely available on the KNMI website .

Besides the Access database (CLIWOC21_97.mdb), the dataset contains the following three (3) files:- CLIWOC 2_1.htm: description in ASCII of the full database (more than 287,000 records) and various versions of the database. Also describes length and format of the records;- imma_format.pdf: documentation of the IMMA format (International Maritime Meteorological Archive), as updated on 14 March 2007;- CLIWOC21.zip: contains 'CLIWOC21.txt' file, the core version of the CLIWOC database.