Recent Iberian drought worst in at least three centuries

Desdemona Despair

[cf. Rain in Spain is on the decline]

27 June 2016 (Sinc) – In the Mediterranean Basin, droughts are a recurring phenomenon that negatively impacts society, economic activities and natural systems. No one seems to doubt the fact that temperatures all over the world have risen in recent decades. However, this trend does not appear to be perceived as clearly when it comes to precipitation (for which data from 1950 onwards is available).

Thus, up until now, the study on the recurrence and severity of droughts in Spain has been based on information from weather stations, with sufficient data only as of the mid-twentieth century.

To test the evolution of the droughts, scientists from the Department of Geography at the University of Zaragoza utilised indirect information, such as the study of tree growth rings, to reconstruct the climate of the Iberian Range as far back as 1694 and to analyse dry periods using the Standardised Precipitation Index (SPI).

The researchers collected 336 samples and 45,648 growth rings from five different species (P. sylvestris, P. uncinata, P. nigra, P. halepensis, and Pinus pinaster) from 21 locations in the province of Teruel, in the east of the Iberian Peninsula, at an average altitude of 1,600 metres.

The results, published in the International Journal of Biometeorology, made it possible to evaluate droughts from the last three centuries; they reveal that the twelve months leading up to July 2012 were the driest over the entire period studied. “We have been able to successfully identify seven especially dry periods and five wet periods since the end of the 17^th century”, says Ernesto Tejedor, the main author of the study, to Sinc. The driest periods

According to the researchers, in addition to these periods there have been 36 extremely dry years and 28 very wet years since the end of the 17^th century. “Some of these dry years, such as 1725, 1741, 1803 and 1879, are also identified in other drought reconstructions in Romania and Turkey, thus demonstrating the larger-scale coherence of the extreme deviations and their relationship with increasingly global atmospheric processes”, adds Tejedor.

Many of these extreme events are associated with catastrophic historical and cultural changes from the last three centuries. In fact, 1725 is known as “The year without a harvest” in Monegros. These events are reflected in historical documents as the “pro-pluvia” rogations, “since the intense droughts led to bad harvests with serious consequences for society”, comments Tejedor.

The reconstruction of droughts using dendrochronology does not make it possible to directly predict extreme future events, although these reconstructions are indeed used to validate future climate change models. “What we are seeing from the 20^th century, and what we have seen so far in the 21^st, is an increase in the recurrence of extreme phenomena, including both wet and dry years”, stresses the researcher to Sinc.

For the expert, predictions for precipitation variability and trends are not yet reliable like those for temperature, as other factors which are still being studied also play a role.

Radiography of drought periods in Spain from the last 318 years

ABSTRACT: Droughts are a recurrent phenomenon in the Mediterranean basin with negative consequences for society, economic activities, and natural systems. Nevertheless, the study of drought recurrence and severity in Spain has been limited so far due to the relatively short instrumental period. In this work, we present a reconstruction of the standardized precipitation index (SPI) for the Iberian Range. Growth variations and climatic signals within the network are assessed developing a correlation matrix and the data combined to a single chronology integrating 336 samples from 169 trees of five different pine species distributed throughout the province of Teruel. The new chronology, calibrated against regional instrumental climatic data, shows a high and stable correlation with the July SPI integrating moisture conditions over 12 months forming the basis for a 318-year drought reconstruction. The climate signal contained in this reconstruction is highly significant (p 

Tree-ring-based drought reconstruction in the Iberian Range (east of Spain) since 1694