The expectation of future precipitation change over the Mediterranean region is different from what we observe

Abstract

In this study we assess the role of anthropogenic forcing (greenhouse gases and sulphate aerosols, GS) in recently observed precipitation trends over the Mediterranean region. We investigate whether the observed precipitation trends (1966-2005 and 1979-2008) are consistent with what 22 models project as response of precipitation to GS forcing. Significance is estimated using 9,000-year control runs derived from the CMIP3 archive. The results indicate that externally forced changes are detectable in observed precipitation trends in winter, late summer and in autumn. Natural internal climate variability cannot explain these changes. However, the observed trends (derived from 3 sources) are markedly inconsistent with expected changes due to GS forcing. While the influence of GS signal is detectable in winter and early spring, observed changes are several times larger than the projected response to GS forcing. The most striking inconsistency, however, is the contradiction between projected drying and the observed increase in precipitation in late summer and autumn, irrespective of the data set used. Natural (internal) variability as estimated from the models cannot account for these inconsistencies, which are already present in the large scale circulation patterns (Geopotential height at 500 hPa). The obtained results are robust to the removal of the fingerprint of the North Atlantic Oscillation. The detection of an outright sign mismatch of observed and projected trends in autumn and late summer, leads us to conclude that the recently observed trends can not be used as an illustration of plausible future expected change in the Mediterranean region. These significant shortcomings in our understanding of recent observed changes complicate communication of future expected changes in Mediterranean precipitation.

Long-term climate change in the Mediterranean region in the midst of decadal variability

“…Inconsistencies between recently observed and projected precipitation trends over the Mediterranean were also found by other studies (e.g. Barkhordarian et al 2013). These results could be due to the impact of internal variability on the computation of the observational trends.…”

Drought-induced changes in the phenology, productivity and diversity of Spanish fungi

“…The Mediterranean basin has been identified as a hotspot of future drying in response to rising greenhouse gases (Kelley et al 2012;Hoerling et al 2012;Barkhordarian et al 2013).In seeking to prevent ecological and financial loss under predicted climate change, we suggest summer irrigation and stand thinning to reduce direct and indirect water competition within and between the host vegetation and its symbiotic fungal partners (B€ untgen et al 2014). Moreover, future forest management strategies aimed at safeguarding prosperity in an era of rapid drying (i.e.…”

“…State-of-the-art model simulations further predict a continuation of this trend in response to rising concentrations of greenhouse gases (Kelley et al 2012;Hoerling et al 2012;Barkhordarian et al 2013). Indications of ongoing and projected climate change are strongest for the Iberian Peninsula (B€ untgen et al 2012a, 2013a), where future rates of temperature increase and precipitation decrease will most likely accelerate aridification (Fischer & Sch€ ar 2010;Xoplaki et al 2012).…”

Potential of microwave observations for the evaluation of rainfall and convection in a regional climate model in the frame of HyMeX and MED-CORDEX

“…There are gaps in our understanding of the processes controlling the Mediterranean precipitation which limit our ability to simulate properly its variability and trend in a warming climate (e.g., Barkhordarian et al, 2013). Such limitations are partially caused by the contribution of fine-scale processes (Rysman et al, 2016) and their non-linear interactions with largescale processes as well as the complex and not well known interactions between oceanic, atmospheric and hydrological processes (e.g., Funatsu et al, 2009;Berthou et al, 2015).…”