Spain: towards a drier and warmer climate?

The study of the precipitation regime aims to verify the hypothesis about the decrease of rainfall in Spain. Is the climate of peninsular Spain and the Balearic Islands moving towards a drier and drier climate?

In principle, global warming (GW), at the planetary level, represents an increase in precipitation. The progressive increase in temperature causes greater evaporation, and therefore greater humidity in the atmosphere, which should produce increasing precipitation. However, this trend is not occurring homogeneously. The various scenarios developed by the IPCC suggest that in Mediterranean latitudes the GW generates a tendency towards greater drought.

One of the objectives of this work is to analyze whether, in Spain, there is a temporal evolution of the precipitation regime towards less precipitation, as well as to study the relationship between annual precipitation and the trend towards progressive warming. Specifically, to verify the hypothesis that the increase in temperature resulting from the GW process implies a trend towards progressive drought.

Two different databases are used in this work: on the one hand, the information provided by AEMET from a selection of meteorological stations throughout Spain, with the daily series of precipitation (rr) and maximum (tx) and minimum (tn) temperatures, from January 1, 1971 to December 31, 2023; on the other hand, information from the Copernicus climate service. Specifically, the one resulting from E-OBS, from January 1, 1950 to December 31, 2022 with a resolution of 0.25 degrees.

In addition to multiple regression, the techniques used are the Mann-Kendall test and the Kendall-Theil-Sen regression.

The Mann-Kendall test confirms the statistical significance of the relationship between rr and tx, with a statistical reliability close to 99.9%. The KTS regression predicts a reduction of 38.49 mm for each 1°C increase.

If the warming trend experienced in recent years (1973-2022) continues, it is foreseeable that by 2050 there will be a reduction in precipitation in Spain of between 14% and 20% with respect to current precipitation (understood as the average between 2000 and 2022). Spain's climate is likely to vary from a Mediterranean climate to a warm steppe climate in the Köppen classification system.