Climate Warming in the Spanish Mediterranean: Its Magnitude and Nature

Abstract

This piece of research completes the line of work on the thermal evolution of the Mediterranean region initiated in the National Plan on Climate Change. The study was undertaken to analyse the active regional thermal series over the 1950–1996 period, rigorously treated by the SNHT (Standard Normal Homogeneity Test) method. This research concluded that the evolution of the mean annual temperatures recorded in the major historical network of Spanish Mediterranean observatories exhibits a significant warming trend. However, analysis of the non-climatic processes, such as the urban effect and weather station relocations, allowed us to conclude (in a study published in 2004) that the assumption of temperature stability in the Spanish Mediterranean should therefore not be rejected. Conclusions that were partially verified in 2016, in particular of the true the urban effect, about the period (1950-2013). The results obtained showed that this magnitude could account for between 70 and 80% of the recorded warming trend in Western Mediterranean cities. In this context, twenty years after the end of the Plan Nacional del Clima, it would be wise to revisit, in 2019, the validity of the conclusions that the regional climate offered. This piece of research aims to assess the true magnitude of the climate warming recorded in the Spanish Mediterranean region. The evaluation is based on the records of 23 observatories belonging to the Spanish regional network of the State Meteorological Agency (AEMET), with complete series covering the 1950–2018 period, processed by the SNHT. The verification is further based on three new analyses. The first involves the analysis of the thermal evolution (1906-1925 and 1991-2018) at the observatory on the Columbretes Islands (28 miles off the coast of Castellón). The island climate series entails in-depth revision of the conclusions and trends set out in our previous studies. The second piece of research involves the magnitude of the Urban Heat Island (UHI, 2001–2018) using temperature records from seven weather stations located in the Castellón-Almassora urban area. The third piece of research was based on the analysis of a trend value that has stabilized since 2010, simultaneously to the decline of the population and the descent of total energy consumption. Therefore, this piece of work verifies the importance of the UHI and establishes the magnitude of the real t regional warming. The study suggests that the real value of climate warming in the Spanish Mediterranean region may be estimated at between 1ºC and 1.1ºC in the period from 1950 to 2018.