Obtaining meteorological data from historical newspapers: La Integridad

The recovery of meteorological data from old documentary sources is of great significance for meteorological and weather research. We describe our recovery of a meteorological series from the late nineteenth and early twentieth century from the pioneering A Guarda Observatory in Galicia (Spain). Data series were obtained from meteorological notes appearing in the newspaper La Integridad as published at the time. In total, we recovered data from over 5000 newspapers using more than 60 000 individual measurements. The recovered variables include temperature, pressure, wind, relative humidity, vapour pressure, evaporation, precipitation, and general weather observations. The recovered data allow us to obtain an overview of the weather for this period in the studied region, as well as to validate and complement other independent data sources and to investigate variations that could be related to anthropogenic climate change. The resulting data are now in digital format and have been released for the wider use of the international scientific community and the general public. We also prove the reliability of meteorological forecasts published from time to time in the same newspaper using historical sea-level pressure data. Finally, we introduce new ozone records reconstructed from the recovered data; these too have huge potential for future climatological and weather research.