Long-term precipitation in Southwestern Europe reveals no clear trend attributable to anthropogenic forcing

D Peña-Angulo,M Tomas-Burguera,F Domínguez-Castro,I Noguera,C Murphy,F Reig,S M Vicente-Serrano,M Aznárez-Balta,Y Tramblay,R M Trigo,M Y Luna,R García-Herrera,A El Kenawy,M Turco

doi:10.1088/1748-9326/ab9c4f

Abstract

We present a long-term assessment of precipitation trends in Southwestern Europe (1850–2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments. Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region. Rather, significant trends were mostly found for shorter periods, highlighting the prevalence of interdecadal and interannual variability at these time-scales. Global climate model outputs from three CMIP experiments are evaluated for periods concurrent with observations. Both the CMIP3 and CMIP5 ensembles show precipitation decline, with only CMIP6 showing agreement with long term trends in observations. However, for both CMIP3 and CMIP5 large interannual and internal variability among ensemble members makes it difficult to identify a trend that is statistically different from observations. Across both observations and models, our results make it difficult to associate any declining trends in precipitation in Southwestern Europe to anthropogenic forcing at this stage.

Highlights

A wide range of studies have reported a decrease in average precipitation in Mediterranean regions, with pronounced drying observed since the 1960s (Longobardi and Villani 2010, Gudmundsson and Seneviratne 2016)
We present a long-term assessment of precipitation trends in Southwestern Europe (1850–2018) using data from multiple sources, including observations, gridded datasets and global climate model experiments
Contrary to previous investigations based on shorter records, we demonstrate, using new long-term, quality controlled precipitation series, the lack of statistically significant long-term decreasing trends in precipitation for the region

Summary

Introduction

A wide range of studies have reported a decrease in average precipitation in Mediterranean regions, with pronounced drying observed since the 1960s (Longobardi and Villani 2010, Gudmundsson and Seneviratne 2016). Other studies have attributed this decline in average precipitation and the corresponding increase in the frequency of dry events to anthropogenic forcing in the Mediterranean area or in Southern Europe (Hoerling et al 2012, Barkhordarian et al 2013, Gudmundsson and Seneviratne 2016). D Peña-Angulo et al Europe, inducing significant streamflow decreases over large parts of the region It is well-recognized that observed hydroclimatic trends are largely influenced by the study period (Hannaford et al 2013). Decreasing trends in precipitation for Southwestern Europe since the 1960s may be seen in the context of long-term climate variability rather than anthropogenically forced change. Some studies have indicated that a considerable percentage of precipitation series in Southwestern Europe may be impacted by data errors, incompleteness, and/or temporal inhomogeneities, which could bias identified trends (Gonzalez-Rouco et al 2001, Begert et al 2005, Gonzalez-Hidalgo et al 2011, Reiser and Kutiel 2011, Turco and Llasat 2011)

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