Fri, 02 Jan 2009 16:02 UTC
Historical documents such as the records of rogativas (ceremonies with origins dating back to Roman agricultural rites) compiled at the Cathedral of Toledo and municipal churches, have allowed researchers to gain an insight into the climatological period between 1506 and 1900 in Toledo and Madrid, particularly in regard to extreme weather events such as droughts.
After processing this information, the scientists published their work in Global and Planetary Change. Their article shows that droughts in Spain throughout most of the 16th Century were infrequent and shorter than in subsequent periods. The period between 1676 and 1710 was characterised by lower hydric stress, and the 19th Century experienced a low frequency of droughts. However, "the most severe droughts were recorded during the period from the end of the 16th Century up until the 18th Century", Juan I. Santisteban, one of the authors of the study and a researcher at the Complutense University of Madrid (UCM) tells SINC.
The researchers discovered that "droughts were more frequent and stronger than in other periods" in the centre of the peninsula during the Little Ice Age, a period covering the time period studied. Although drought intensity was similar to present-day levels, the study was unable to clarify whether current droughts last longer than previous ones, "even though the greater demand for water today makes the lack of water seem so severe", says Santisteban.
The study also checked the results against those obtained from other records in the Mediterranean area. "Notable differences can be observed between the frequency and duration of droughts - we find rainy periods and droughts at the same time in different parts of the Iberian Peninsula and also differences between northern and southern parts," points out Santisteban.
The combined analysis of this drought information and of atmospheric pressure at sea level - carried out by researchers from the UCM, the Geological and Mining Institute of Spain, and the University of Barcelona - shows that periods of frequent droughts coincide with positive phases of the North Atlantic Oscillation (NAO), which produces prolonged anti-cyclonic conditions in the Azores. However, they add that "the topography of the Iberian Peninsula could be largely responsible for much of the heterogeneity of the drought phenomenon".
The Church, tracking the climate
Ceremonies carried out at the Cathedral of Toledo were controlled by strict protocols set by the Church, and varied according to the gravity of meteorological conditions. In Spain, the cathedral archives of many dioceses hold relatively continuous records from the 16th Century onwards.
The data on rogativas analysed by the scientists come from three sources - the 121 volumes of capitulary records from the Cathedral of Toledo, which record daily life from 1466 to 1599, the book started by Juan Bautista de Chaves Arcayos (who summarised the capitulary books from 1434 to 1599 and incorporated his own updates), and the 331 volumes of capitulary books (1464-1914), which fill in the gaps between the capitulary records.
This series of rogativas contains 341 prayers for rain, 36 pro-serenitate prayers for fine weather, and 94 Masses of thanks (ceremonies to celebrate the ending of the climatological phenomenon that had necessitated the rogativa). Many of the rogativas were part of Spring ceremonies.
Domínguez-Castro, Fernando; Santisteban, Juan I.; Barriendos, Mariano; Mediavilla, Rosa. Reconstruction of drought episodes for central Spain from rogation ceremonies recorded at the Toledo Cathedral from 1506 to 1900: A methodological approach. Global and Planetary Change, 63(2-3) Sp. Iss. SI: 230-242 SEP 2008