The Importance of Long Climate Records (Second Edition)

Dear Colleagues,

It is pertinent to celebrate past weather records, as they are vital in helping us identify aspects of climate change. The earliest temperature records and international network of meteorological observations, the Rete Medicea, started in 1654, founded by Ferdinand II de’ Medici, the Grand-Duke of Tuscany. Other international networks were organized by the Royal Society, London, in 1723, the Societé Royale de Médecine, Paris, in 1778, and the Societas Meteorologica Palatina, Mannheim, in 1781. Long records help us test hypotheses concerning climate change, where the pattern of change is slow and subtle, as well as new hypotheses when the beginning of a certain set of weather readings is unknown. They help us calibrate proxy series and transform and express them in normal units of temperature, precipitation, or other weather variables, thus extending our knowledge back in time, up until the pre-instrumental period. Early instrumental data are fundamental in reducing uncertainties and better knowing trends, accelerations, and both past and present changes in the climate, including the transition from the Little Ice Age to the pre-industrial situation and present-day global warming. Then, they can also be used to verify climate models, determine risk from extreme events, and improve future climate projections.

However, in the early instrumental period, records were scarce and taken using non-standard instruments and protocols. Methods, observing times, and exposures were different, and, in most cases, metadata are missing. Some international meteorological networks helped researchers adopt uniform practices and instruments. A turning point was reached in 1873, when the International Meteorological Committee was established to coordinate observing methods and protocols, substituted in 1950 by the World Meteorological Organization. The first challenge facing our field is to find and rescue data and metadata in a process whereby original records are catalogued and imaged. Data rescue includes copying, digitizing, archiving, and making early records usable, in cases where the originals were either handwritten, printed, or in graphical form. The next challenge is to recover them by deciphering, interpreting, and transforming early instrumental readings and their metadata to obtain high-quality datasets in modern units. After this process, an early series is ready for analysis to investigate the climate or conduct other studies.

This Special Issue will provide examples of climate change identification across a wide spectrum of weather observations, from temperature, precipitation, and sunshine to atmospheric pressure, wind, snow and ice, visibility, and fog. It will also encourage the discussion of metadata to show that each weather station needs to have strong accompanying records if they are to prove useful in the years and decades to come. In cases where significant changes have occurred and, typically, for all data recorded before the standardization which started with the foundation of the International Meteorological Committee in 1873, homogenization techniques must be employed. Examples of data rescue and recovery will hopefully be included in this Special Issue, as well as the following topics:

• climate change;
• metadata;
• early instruments and screens;
• early observation protocols;
• transformation from early units and time references (e.g., day starting from twilight or from the apparent solar time (AST) to the coordinated universal time (UTC));
• data homogenization;
• proxy and instrumental data calibration, rescue, and recovering.

Prof. Dr. Dario Camuffo
Dr. Francesca Becherini
Dr. Antonio della Valle
Guest Editors

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• long weather records
• climate change
• metadata
• homogenization
• case studies from stations with century-scale records
• recovery of early instrumental observations (e.g., 17th century, 18th century, and first half of the 19th century)
• early instruments, protocols, calibrations, and units
• instrumental and proxy data rescue and recovery
• calibration of proxy and instrumental data

• The Importance of Long Climate Records in Climate (13 articles)