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Exploiting data to explore recent climate trends

Benoît Hervieu
Benoît Hervieu
Journalist at Usbek & Rica

Meteorology is, in part, linked to history, and the history of climatology can help us to better understand climate change. This was the main idea developed by Sylvie Jourdain, of Météo France’s Department of Climatology and Climate Services, during the conference Recent climate changes: What data to use? held on 7 March 2017 at the Musée des Archives Nationales in Paris, and sponsored by BNP Paribas Foundation. Her timely lecture was addressed to a full audience.

Two kilometres of meteorological records to serve climate prediction.

In 2011, the National Archives and the public meteorological service forged a partnership to undertake a major inventory of national meteorological archives. One year later, this shared effort was incorporated into the Climate Initiative project through the support of BNP Paribas Foundation

Which data should we focus on? How can we preserve and use it to build knowledge and improve the accuracy of climate forecasts? These major questions shaped Sylvie Jourdain’s lecture, which was broken down into three parts. 

Scale, extent and availability of meteorological measures to study climate

Climate change can be effectively analysed only based on long data series: data established over a long period of time, and standardised as a result. In fact, the instruments of climate observation have themselves evolved over time, especially with regard to remote sensing and theoretical studies enhanced by climate simulation models. For long-term analysis, it is necessary to use biogeochemical and physical climate measures; in other words, direct information from measurements of temperature, pressure, rainfall and other parameters.

Birth of radiosonde, first balloon throws with radiosonde at the Observatoire de Trappes in the early 1930s © Météo-France / Archives nationales

In Europe, the first systematic measurements date back to the 17th century. In France, the first meteorological network was established in 1776 by the Royal Society of Medicine. This capacity for climate observation was further developed in 1830 under the initiative of the Marine Network of Colonial Hospitals, and eighty years later, through the expansion of the network linked to the Paris Observatory. Accordingly, the French meteorological database has grown by 132 million station-days since 1780, of which 21% are from between 1800 and 1949. 

From 1850 on, the data allowed for the reconstruction of long series with the potential to support analyses and forecasts. A reconstructed curve of average temperatures recorded in the northern hemisphere, up to and including the year 2016, highlights the reality of global warming: 2015 and 2016 were far and away recorded as the warmest on record. 

Historic national meteorological records of the National Archives

For a long time, all of this data was unused and stored in boxes at the Fontainebleau site of the National Archives, in a building known as “Le Peigne”: a total of 6,300 boxes, or two kilometres. These boxes contain a massive number of administrative and projection archives. The METC climate archives containing observation records take up 4,300 cartons alone. Add to these 1,345 additional boxes of daily reports: handwritten notes, maps, watercolours, photographs, diagrams and other inspection records.

This treasure accumulated over time as the meteorology service deposited the boxes between 1971 and 1992. Until 2012, the records were very scarcely used. For a long time, the lack of technological means was the primary barrier; soon, the necessary removal of asbestos will represent a new obstacle.


Four major priorities are on the agenda moving forward. The first consists in promoting the value of the meteorological records. To this end, a joint scientific research agreement for the preservation of historical meteorological data will soon be signed by Météo France and the National Archives. Closely related to the first, the second priority is to promote the value of meteorological records in former colonies. An initiative is planned to this effect in Madagascar, with the support of the World Meteorological Organisation.

Though more technical, the two remaining priorities are of no less importance. The third focuses on extending, completing and even constructing instrumental long series of centennial reference observations. These long series will contribute to scientific research and international data sets. Finally, the highly anticipated publication of the digitised archives is on the agenda. It will include the Météo France records and the national meteorological records deposited at the National Archives. It will take the form of a digital library based on a management system for both physical and digitised documents

The amount of data is immense, and much of it has yet to be explored.

France, like Great Britain, possesses a broad archival potential that can be explained, in part, by the reach of its territory in the colonial era. Can this mine of information be considered an example of heritage, as defined by the domains of art and culture? It does, indeed, represent a scientific heritage with an historical dimension, as emphasised by Sylvie Jourdain. Though necessarily incomplete, her lecture allowed us to trace the historic influence of the “anthropogenic forcing”1 (pollution, greenhouse effect) that has become an issue of widespread concern.

(1) Negative externality of energy produced (Thierry Keller)

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