Naval historians and novelists have found the first-hand comments of daily life in the 'wooden world' to be a rich source of knowledge and information. However, only recently have scientists turned their attention to the weather data so assiduously gathered in these venerable documents.

Image of Earth courtesy of NASAToday, global warming and climatic change is a major environmental concern. In order to estimate how the future may unfold, we need to know more about the climatic changes that have occurred in the past. Instrumental records provide a global picture only over the past 150 years, although some local records go back much further. The Central England temperature series is the longest if its kind, but applies only to part of Britain. We have little information on the seas and oceans that cover three-quarters of the Earth's surface. The data contained in the logbooks can help to fill this huge gap as scientists have begun to appreciate how closely the climate is governed by the oceans.

From the mid-19th century logbooks recorded useful instrumental data such as sea and air temperatures, air pressure, wind direction and wind strength. However, data from earlier periods has been almost completely overlooked. There are a number of reasons why such a rich source of information has been neglected:

• The data is non-instrumental and based on the observations and estimates of wind force, wind direction and state of the sea and sky, and some scientists retain an unreasonable prejudice against such information.
• Logbooks are written in the curious style and vocabulary of mariners of those distant times and are not always easy to read and understand.
• The very large numbers of logbooks that have survived present a challenge, not of data shortage, but of over-abundance, requiring huge logistical effort to gather and collate even a fraction of the vast volume of data that they contain.

Obstacles have to be overcome in the extraction, collation and analysis of such non-instrumental data, but the abundance of data for wind force and direction is invaluable. It tells us much about the broad patterns of atmospheric behaviour related to the high and low-pressure systems. These systems govern the everyday weather that we recognise as rainfall, snow, temperatures, cloud and sunshine. In that sense the data can be regarded as more fundamental to our understanding of climate than are instrumental data such as temperature and rainfall measurements.