Objectives

Extreme climate conditions have always had political, economic and social impacts, the nature and severity of which have varied between regions, societies and periods. In a context of climate change, marked by an expected increase in the frequency and severity of such phenomena, the ability to understand the evolution and the material, economic and social impacts of past extreme climate conditions may prove to be a valuable aid for future decisions relating to adaptation strategies. The RENASEC project was devised with this objective in mind: the existing catalogue and description of the extreme events that have occurred in several vulnerable regions of France since 1500 will be used to:

• Determine whether the severity and frequency of extreme phenomena have indeed been altered by the climate change currently underway, as forecast by the models;
• Assess the ecological, material, economic and social impacts of these extreme climate events and analyze how they prompted the adoption of prevention and assistance policies after they occured;
• Create a model representing the cost of major extreme events, which could be used to improve our assessment of future damage if such events were to increase in frequency and severity. 

Methodology

Geographical framework

The geographical framework for this research was chosen such that it is representative of the major climate areas of France and the main extreme phenomena, as well the main environmental features and socioeconomic situations. It will cover the following regions:

• Western France (including the former provinces of Britanny and Normandy), for flooding and storms at sea;
• Eastern France (covering Alsace, Lorraine and Franche-Comté), a heavily-forested region that is ideal for observing storm- and snow-related phenomena;
• Rhône-Alpes, a region known for its flooding, ice jams and snowfall;
• Languedoc-Roussillon, a region regularly affected by drought and floods;
• Ile-de-France (Paris region), which is frequently struck by extreme phenomena such as flooding and ice break-up, droughts in Beauce, storms, etc.

Calendar

Part 1: Centralization and analysis of data relating to the five selected geographical sites obtained from a corpus of archive documents

The "livres de raison" (family record books) in which aristocrats and bourgeois citizens traditionally recorded everyday events contain numerous allusions to unusual climate events.

Religious documents (such as parish registers and descriptions of processions against meteors) also occasionally mention climate events.

The archives produced by the various royal and republican government agencies contain a wealth of information:

• Forestry and maritime legal archives, for example, are essential resources for studying storms and coastal submergence;
• Historical provincial government records contain a great deal of information relating to the history of natural risks in pre-revolutionary France, such as the results of surveys conducted in the communities of avalanche or flood victims, and applications for tax relief following hailstorms, floods, forest fires and harsh frosts.

Cartographic sources, and in particular the military maps produced from the late 17^th century onward.

Part 2: Creation of a climate database

The contents of this corpus provide a reliable record - in terms of both description and duration - of four types of extreme climate phenomena: flooding, droughts, ice jams/breakup and storms. This is because the dates, duration and precise location of these phenomena have been recorded in the archives since 1500. The information obtained by analyzing these documents will be added to a climate database, specifying the event type, date, source and location, together with a full description drawn from the archives.

Part 3: Relative estimate of the severity of the 4 types of extreme

When the database has been compiled, a more quantitative approach will be adopted as part of a broader climate-focused effort to assess the severity of observed (but unmeasured) extreme events. Reliable instrumental data (such as thermometer or barometer readings) for extreme events was not available prior to the 1750's. A method of relative quantification must therefore be developed.
For the specific case of storms and hurricanes, consideration is being given to the application of the Beaufort scale to events predating the 19th century. This tool, which was created in 1805, estimates wind speeds on a scale from 0 to 12, based on the wind's observed effects on land and at sea. The forestry descriptions available for the 1500's to 1800's contain sufficiently detailed information (including the nature and extent of the areas devastated by extreme events) to allow an interpretation to be made based on the Beaufort wind scale.

Part 4: Development of a model to represent the cost of major extreme events

Major natural disasters having dramatic effects on affected populations have been extensively documented since the 1500's. The construction of the modern State, which claimed the authority to override other local powers such as the clergy and the nobility in crisis situations, saw the introduction of specialized government agencies (Eaux et Forêts, Ponts et Chaussées, admiralties, records offices and more recently prefectures) with responsibility for the management of natural risks among other duties. In their efforts to develop a model representing the cost of major extreme events, historians will have access to damage inspection reports, investigations and counter-investigations resulting in direct aid, such as the mobilization of human resources (e.g. soldiers and engineers), or indirect assistance (e.g. tax relief). This wealth of documentary evidence will make it possible to "weigh up" the total cost of such disasters, expressed, as appropriate, in man-days of work, as a percentage of the royal budget, or, from the 19th century, in francs (convertible to euros). This work will be conducted jointly with the economists at CIRED.
It will be possible to use the cost model thus developed to estimate the economic impact of future damage if extreme climate events were to increase in frequency and severity. The results of this research may form the basis for implementing adaptive measures and measures to reduce greenhouse gas emissions.