Climate change in mediterranean climate-type zones


Mediterranean climate is characterized by mild, wet winters and hot, dry summers thus making the interested climatic zones among the most desirable for human inhabitation. Mediterranean climate zones are located in transitional midlatitude regions like the Mediterranean basin area, western North America as well as over small areas of western South America, Southern Africa and southern Australia. This classification based on Koppen-Geiger approach is well suited for identifying and analyzing the impacts of climate change on natural and anthropic ecosystems. The transitional character with sharp spatial gradients makes Mediterranean climate-type zones highly vulnerable to climate change. Future climate projections indicate an intensification of the seasonality over these regions, as well as potential migration of these climate regions towards the poles with the equatorward margins likely replaced by arid climate-type. For all mediterranean climate-type regions, the future is expected to provide large issues to face for biodiversity and water availability, including climate adaptation and mitigation measures.
This session aims bringing together studies on different aspects of climate and climate change focused on the Mediterranean climate-type regions of the world. Physical (including extremes, teleconnections, hydrological cycles) and biogeochemical (including biodiversity) approaches but also social aspects (including impacts and adaptation measures) are welcome, either in terms of observed past changes or future climate projections.

Solicited Speaker will be Prof Don McFarlane - School of Agriculture and Environment, University of Western Australia

Convener: Annalisa Cherchi | Co-conveners: Andrea Alessandri, Annarita Mariotti, James Renwick
vPICO presentations
| Fri, 30 Apr, 09:00–09:45 (CEST)

vPICO presentations: Fri, 30 Apr

Chairpersons: Annalisa Cherchi, James Renwick
Don McFarlane

Climate change has profoundly affected the hydrology of south-western Australia since at least 1975. It took over a decade before the signal could be detected from annual variability. The impacts of rainfall reductions were exacerbated by higher temperatures and a decrease in wet periods when most recharge and runoff occurred. As a rule-of-thumb, runoff and recharge reduced by 3 percent for each percent reduction in rainfall.

Reductions in runoff were driven by falling groundwater levels. Stream- and dryland-salinity required levels be monitored, otherwise this driver would have gone unnoticed.

Runoff into reservoirs has almost ceased as processes irreversibly changed. Using historical records to estimate future runoff had limited application because of non-stationary processes.

While water resources have diminished, the threats posed by dryland salinity, stream salinity, flooding and waterlogging have decreased. While winter flood risks have dramatically reduced, summer flood risks appear to have increased.   

Almost all GCMs project an even drier and warmer future. Perth (population 2m) has avoided a ‘Day Zero’ by the rapid expansion of shallow- and deep-groundwater extraction, and seawater desalination. Highly treated wastewater has started to be added to augment drinking water aquifers.

Recharge under tree canopies have been most reduced. This is due to greater interception losses because showers have largely replaced heavy rain, and trees using a higher proportion of rainfall. Rainfall intensities, at least for long durations, have decreased despite the fear that higher sea surface temperatures (SST) and a warmer atmosphere will result in more intense rainfall. While SSTs have started to rise, there are complications related to El Niño– Southern Oscillation, the Indian Ocean Dipole and the warm Leeuwin Current that flows down the coast of Western Australia. This current results in much higher rainfall than would be expected and may weaken if El Niño becomes stronger and/or more frequent.  

As well as impacting water resources and rates of land degradation, climate change has affected ecosystems and industries. Abnormally hot and dry years have resulted in the deaths of trees able to withstand harsh Mediterranean summers. Wetlands have dried and groundwater-dependent ecosystems have been lost. Cereal crops are now grown in regions that used to be severely affected by soil waterlogging.  Tree plantations have become unviable due to slow wood growth and deaths.

Water restriction may have exacerbated urban heat islands as outdoor areas are irrigated less often, losing evaporative cooling. Fortunately, there are opportunities for diverting stormwater and treated wastewater to urban aquifers that provide a non-potable source of water for self-supply.

Government regulations and planning that have been set during the pre-1975 climate are struggling to keep pace with changes in understanding and future predictions. Restrictions tackling old problems are not being replaced with those needed for new issues. It is difficult to allocate water on a fixed volumetric basis when runoff and recharge are highly impacted. Society is also having to accept water reuse more quickly than is ideal.   

Lessons learned in SW Australia may be applicable to other Mediterranean climate zones.

How to cite: McFarlane, D.: Climate change impacts on the hydrology of south-western Australia, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-3759,, 2021.

Josep Roca, Blanca Arellano, and Qianhui Zheng

The definition of the building climate zones is the basis for studying the effects of urban climate on building energy consumption and efficiency. In Spain, the transposition of the European Directive on Energy performance of buildings (Directive 2010/31/EU) has been carried out through the Technical Building Code (CTE), which divides the territory into climatic zones through which it evaluates the energy performance of buildings. However, the CTE carries out a climatic division based on administrative criteria ("provinces", NUT3), which leads to oversimplifying the Spanish climatic reality.

In this sense, the paper develops a new methodology for classification maps of climatic zones of buildings in Spain in order to improve the CTE. Therefore, the application in Spain of the CTE, Köppen and ANSI / ASHRAE methodologies are critically studied and compared. A first approach shows inadequacies that could be improve to optimize the energy efficiency of buildings. The climatic data for Spain -provided by the European Climate Assessment & Dataset Project ( since 1950 (with a resolution of 1 km2/pixel) are analyzed, and a series of climatic indicators are established (such as the number of summer days, tropical nights, heating degree days, …). Next, OLS and cluster analysis are used as a method to define the Spanish climatic zones. Finally, the research proposes a new climate zones classification for Spain. The new classification provides more detailed climate information for building energy efficiency research and improves the classification defined in the CTE.

How to cite: Roca, J., Arellano, B., and Zheng, Q.: Climate Zones Classification for Buildings Energy Efficiency Assessment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4765,, 2021.

Giuseppe Zappa, Paulo Ceppi, and Theodore Shepherd

Regions with a Mediterranean-like climate, apart for California, are projected to receive less rainfall due to climate change, thus posing serious implications for future water availability for societal and agricultural needs. At a first order, it is often assumed that water availability is proportional to global mean warming. Yet, the mechanisms controlling the precipitation response in Mediterranean climates remain only partly understood, as shown by the substantial uncertainty that still characterises the climate model projections. Here, by analysing projections from the CMIP5 climate models, we show that the linear scaling with warming does not apply in three key Mediterranean-like regions, namely Chile, California and the Mediterranean proper. In particular, despite long-term warming, the models show that the projected precipitation reduction in Chile and the Mediterranean halts as soon as anthropogenic forcing is stabilised, while the precipitation increase in California accelerates. By examining the response to an abrupt quadrupling of CO2, we demonstrate that such non-linearity in the time-evolution of precipitation cannot be solely explained by the well-known rapid adjustment to radiative forcing, but it is instead due to distinct fast and slow patterns of atmospheric circulation change, that are themselves forced by the time-evolution in the spatial patterns of sea-surface temperature warming. In particular, while the fast warming is favourable to force a poleward shift of the mid-latitudes jets, hence drying the Mediterranean and Chile, the slow warming, including an el nino-like pattern in the tropical Pacific, inhibits such shifts and precipitation changes, while favouring the wetting of California. The results show that stabilising GHG concentrations will have an immediate benefit to the hydro-climate of these Mediterranean-like regions, while pointing to constraining uncertainty in the patterns of surface warming as an important step to increase confidence in the future projections. 

How to cite: Zappa, G., Ceppi, P., and Shepherd, T.: Time-evolving sea-surface warming patterns modulate the climate change response of precipitation in Mediterranean-like regions, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-13493,, 2021.

Roman Brogli, Silje Lund Sørland, Nico Kröner, and Christoph Schär

It has long been recognized that the Mediterranean is a ‘hot-spot’ of climate change. The model-projected year-round precipitation decline and amplified summer warming are among the leading causes of the vulnerability of the Mediterranean to greenhouse gas-driven warming. We investigate large-scale drivers influencing both the Mediterranean drying and summer warming in regional climate simulations. To isolate the influence of multiple large-scale drivers, we sequentially add the respective drivers from global models to regional climate model simulations. Additionally, we confirm the robustness of our results across multiple ensembles of global and regional climate simulations.

We will present in detail how changes in the atmospheric stratification are key in causing the amplified Mediterranean summer warming. Together with the land-ocean warming contrast, stratification changes also drive the summer precipitation decline. Summer circulation changes generally have a surprisingly small influence on the changing Mediterranean summer climate. In contrast, changes in the circulation are the primary driver for the projected winter precipitation decline. Since land-ocean contrast and stratification changes are more robust in global climate simulations than circulation changes, we argue that the uncertainty associated with the projected climate change patterns should be considered smaller in summer than in winter.


Brogli, R., S. L. Sørland, N. Kröner, and C. Schär, 2019: Causes of future Mediterranean precipitation decline depend on the season. Environmental Research Letters, 14, 114017, doi:10.1088/1748-9326/ab4438.

Brogli, R., N. Kröner, S. L. Sørland, D. Lüthi and C. Schär, 2019: The Role of Hadley Circulation and Lapse-Rate Changes for the Future European Summer Climate. Journal of Climate, 32, 385-404, doi:10.1175/JCLI-D-18-0431.1

How to cite: Brogli, R., Lund Sørland, S., Kröner, N., and Schär, C.: Large-scale drivers of the Mediterranean climate change hot-spot, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-4546,, 2021.

Hossein Alilou, Matt Hipsey, and Carolyn Oldham

Numerous studies have highlighted the rapid pace of climate change in South Western Australia and quantifying hydrological shifts may provide insights into climate impacts in other Mediterranean regions. Identifying connections in data from spatially distributed rainfall stations using different interpolation approaches, can fill gaps in historical datasets and allow effective installation of new rain gauges based on optimal density and location. Different insights were revealed by using multiple approaches across the time series: the Seasonal Mann-Kendall Test, the Mann-Kendall Test under the Scaling Hypothesis (MKLTP), the Lanzante’s test (LAT) as single change point detection tests, the E-Agglomerative (ECP) and E-Divisive (EDP) change detection algorithms as multiple change point detection tests. Twenty seven loading factors (e.g. seasonal and annual Sen’s slope, the year and number of change points) were calculated from daily rainfall data collected over 100 years (1920-2019) from 107 meteorological stations in South Western Australia. The results illustrated that the rate of rainfall fluctuation in terms of Sen’s slope varied from -2.6 mm yr-1 in coastal areas to 0.9 mm yr-1 in inland areas. The scaling trend analysis identified that 53% of the stations were effected by long-term persistence in the wet season, in contrast to only 20% in the dry season. The single change point methods identified a change in the 1940s-1950s and the multiple change point methods identified two changes, in the 1940s and 2000s. The spatial correlation of stations were also mapped using an unsupervised machine learning approach (K-Means), the Multiscale Bootstrap Resampling (MBR), and loading factors, into three optimal clusters, indicating that rainfall in the coastal areas continue to decline, whereas rainfall in the inland areas has increased over the previous 100 years. These statistical and machine learning approaches are effective in identifying spatial and temporal variability in climate change trends.

How to cite: Alilou, H., Hipsey, M., and Oldham, C.: Quantifying spatial correlations and trends in rainfall data under a Mediterranean climate using non-parametric statistical and machine learning approaches, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-5701,, 2021.

Josep Cos, Francisco J Doblas-Reyes, and Martin Jury

The Mediterranean has been identified as a climate change hot-spot due to increased warming trends and precipitation decline. Recently, CMIP6 was found to show a higher climate sensitivity than its predecessor CMIP5, potentially further exacerbating related impacts on the Mediterranean region.

To estimate the impacts of the ongoing climate change on the region, we compare projections of various CMIP5 and CMIP6 experiments and scenarios. In particular, we focus on summer and winter changes in temperature and precipitation for the 21st century under RCP2.6/SSP1-2.6, RCP4.5/SSP2-4.5 and RCP8.5/SSP5-8.5 as well as the high resolution HighResMIP experiments. Additionally, to give robust estimates of projected changes we apply a novel model weighting scheme, accounting for historical performance and inter-independence of the multi-member multi-model ensembles, using ERA5, JRA55 and WFDE5 as observational reference. 

Our results indicate a significant and robust warming over the Mediterranean during the 21st century irrespective of the used ensemble and experiments. Nevertheless, the often attested amplified Mediterranean warming is only found for summer. The projected changes vary between the CMIP5 and CMIP6, with the latter projecting a stronger warming. For the high emission scenarios and without weighting, CMIP5 indicates a warming between 4 and 7.7ºC in summer and 2.7 and 5ºC in winter, while CMIP6 projects temperature increases between 5.6 and 9.2ºC in summer and 3.2 to 6.8ºC in winter until 2081-2100 in respect to 1985-2005. In contrast to temperature, precipitation changes show a higher level of uncertainty and spatial heterogeneity. However, for the high emission scenario, a robust decline in precipitation is projected for large parts of the Mediterranean during summer. First results applying the model weighting scheme indicate reductions in CMIP6 and increases in CMIP5 warming trends, thereby reducing differences between the two ensembles.

How to cite: Cos, J., Doblas-Reyes, F. J., and Jury, M.: Mediterranean climate change projections: an update from CMIP5 and CMIP6., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-12803,, 2021.

Ece Yavuzsoy, Yasemin Ezber, and Omer Lutfi Sen

El Nino Southern Oscillation (ENSO) is a phenomenon in the equatorial Pacific that could have profound effects on climate around the world. Although ENSO impacts are fairly well-defined for south and north America, Australia and south-eastern Asia, they are not very clear for Euro-Mediterranean region. Some studies indicate that the negative phase of ENSO in Nino3 and Nino3.4 indices have similar effects in the negative phase of North Atlantic Oscillation (NAO).  ENSO impacts and teleconnection patterns are mostly studied using the Nino3.4 index. However, some recent studies indicate that the Nino1+2 index has higher correlation with climate variability over the Euro-Mediterranean region.

In this study, we investigate impacts of ENSO over the Euro-Mediterranean climate variability and atmospheric dynamics using the Nino1+2 and Nino3.4 indices. Additionally, we also tried to understand if there is any relation between ENSO and the Mediterranean and East Asian troughs. NCEP/NCAR Reanalysis surface air temperature, precipitation and 500 hPa geopotential height datasets and SST-based ENSO indices from ERSSTv4 were used in the analysis for boreal winter (December-January-February) for a period of 1950 - 2019. We utilized the Pearson correlation analysis to reveal the relation between these indices and climate parameters and the composite analysis  to define the pattern differences between the cold and warm phases of the indices.

Our preliminary findings show that there is a distinct correlation pattern between Nino indices and surface air temperature over the region of interest. Nino1+2 index has a more distinct dipole pattern with a significant positive correlation pole over central Europe and negative pole over north-eastern Africa. However, Nino3.4 indicates a rather zonal correlation dipole pattern whose poles are over northwest Africa (strongly positive) and northeast Africa (negative). It is also found that the Mediterranean trough location is sensitive to the phase of ENSO for both indices. Namely, the Mediterranean trough tends to be in the west of its climatological location for La Nina phases of Nino1+2 and Nino3.4, which affects the distribution of surface temperature and precipitation over the Euro-Mediterranean and Middle East and Northern Africa (MENA) regions. We concluded that the La Nina phase of Nino1+2 seems to play a more distinctive role in the dipole pattern. The surface air temperature is colder over the entire Europe while it is opposite in the Middle East region including Turkey. This dipole pattern is also detected for the La Nina phase of Nino3.4, but it is mostly observed over southwestern Europe and northern Africa. Comparison between the La Nina and El Nino phases of the Nino1+2 index indicates that for the La Nina phase precipitation is larger over the Aegean Sea and Italy and smaller in northern Europe.

How to cite: Yavuzsoy, E., Ezber, Y., and Sen, O. L.: Comparison of NINO1+2 and NINO3.4 indices in terms of ENSO effects over the Euro-Mediterranean Region, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1141,, 2021.

Eilat Elbaum, Chaim I. Garfinkel, Ori Adam, and Efrat Morin

Observations from the past century and projections for the end of this century show a decrease in precipitation over the eastern Mediterranean Sea and surrounding land areas. Changes in precipitation are controlled by both thermodynamic and dynamic processes, but the relative contributions of these processes, in particular on regional scales, is not well understood. Models included in the fifth and sixth phases of the Coupled Model Intercomparison Project (CMIP5 and CMIP6) exhibit a wide spread in the magnitude of expected drying in the eastern Mediterranean region, as well as in other meteorological variables. By decomposing projected changes in the moisture budget in 48 models into mean dynamic and mean thermodynamic components, we explore the contribution of each of these components to the model spread in regional drying. In the eastern Mediterranean, the dynamic component explains 64% and the thermodynamic component explains 9% of the variance in net precipitation change. We further examine the relation of the regional components to changes in five large-scale mechanisms: tropical vertical stratification, global near-surface temperature, latitude of the eddy-driven jet, stratospheric polar vortex, and arctic amplification. Of these, we find that a decrease in the dynamical contribution in the eastern Mediterranean, causing regional drying, is most strongly related to a northward shift of the eddy-driven jet and a rise in global near-surface temperature.

How to cite: Elbaum, E., Garfinkel, C. I., Adam, O., and Morin, E.: Eastern Mediterranean Drying: Projected Changes in Dynamics and Thermodynamics and Their Relation to Large-Scale Processes, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-706,, 2021.

Alexander Rischmüller, Alexia Karwat, Richard Blender, and Christian Franzke

Datasets with precipitation indices from the coastal areas of Syria, Lebanon and Israel are defined from the ERA5-Land database (0.1° resolution). In each coastal area the grid point with the highest hourly precipitation is selected. The declustered datasets are modelled by generalised Pareto distribution. The parameters of the stationary models are estimated using the maximum likelihood (MLE) and Bayesian inference methods.

Non-stationary models with several different covariates, i.e., time and teleconnection indices are incorporated into the scale parameter. The parameters of the non-stationary models are estimated using the MLE. The goodness-of-fit of stationary models is assessed by the Anderson-Darling test. QQ-plots subjectively assess the goodness-of-fit for both stationary and non-stationary models. The goodness-of-fit of non-stationary models is assessed in comparison to the stationary models with the likelihood ratio test (LRT) and with the differences in the Akaike information criterion (AIC).

The results show clear non-stationarity with the time covariates. Non-stationarity with teleconnection covariates is incoherent, except for the North Atlantic oscillation (NAO) in Syria. Return levels are estimated for stationary and non-stationary models which are obtained from different quantiles of the time-changing scale parameter vector according to -risk scenarios. The results show that return levels are highest in Syria and lowest in Israel.

How to cite: Rischmüller, A., Karwat, A., Blender, R., and Franzke, C.: Extreme Precipitation in the Eastern Mediterranean in ERA5, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-10019,, 2021.

Diana Mance, Ema Topolnjak, Anita Crnov, Davor Mance, Maja Radišić, and Josip Rubinić

The highest average annual rainfall in Croatia is in the Northern Adriatic, with some parts of the region receiving more than 2000 mm per year. Characteristics of the region’s weather are periods of intense rain alternating with dry periods in which the amount of precipitation can be negligible for more than a month. The area's water supply relies on karst groundwater sources that are primarily fed by Mediterranean precipitation. The aforementioned precipitation regime results in high groundwater yields in the cold part of the hydrological year and substantially decreased water quantities in the summer months. Under such specific conditions, it is of considerable importance to find out about the potential for climate change in order to ensure timely adjustment of the management and use of natural sources of water.

We present a comparison of the isotopic composition of precipitation collected on the mountain Učka in periods 2008-2011 and 2019-2020. Rain gauges were located on a vertical gradient from sea level up to nearly 1400 m. Unlike the isotopic altitude effect that did not change significantly compared to the one reported for the first period (Roller-Lutz et al, 2013), the weighted means of isotopic values were more positive in the second period.  For the cold part of the hydrological year, local meteoric water line has recently moved to higher values, indicating the sources of precipitation from drier Mediterranean regions. Local meteoric water line for the warm part of the last hydrological year, indicates presence of increased evaporation and thus confirms lower precipitation amounts.


Roller-Lutz Zvjezdana, Mance Diana, Hunjak Tamara, Lutz Hans O. (2013) On the isotopic altitude effect of precipitation in the Northern Adriatic (Croatia), Isotopes in Hydrology, Marine Ecosystems and Climate Change Studies. Vol. I. Proceedings of an International Symposium


This work was supported by the University of Rijeka as part of the research project uniri-pr-prirod-19-24.

How to cite: Mance, D., Topolnjak, E., Crnov, A., Mance, D., Radišić, M., and Rubinić, J.: Stable isotope composition of precipitation as signal of possible climate change: the case of the mountain Učka (Northern Adriatic, Croatia), EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-164,, 2021.

Thibault Mathevet, Cyril Thébault, Jérôme Mansons, Matthieu Le Lay, Audrey Valery, Agnès Brenot, and Joel Gailhard

The aim of this communication is to present a study on climate variability and change on snow water equivalent (SWE) and streamflow over the 1900-2100 period in a mediteranean and moutainuous area.  It is based on SWE and streamflow observations, past reconstructions (1900-2018) and future GIEC scenarii (up to 2100) of some snow courses and hydrological stations situated within the French Southern Alps (Mercantour Natural Parc). This has been conducted by EDF (French hydropower company) and Mercantour Natural Parc.

This issue became particularly important since a decade, especially in regions where snow variability had a large impact on water resources availability, poor snow conditions in ski resorts and artificial snow production or impacts on mountainous ecosystems (fauna and flora). As a water resources manager in French mountainuous regions, EDF developed and managed a large hydrometeorological network since 1950. A recent data rescue research allowed to digitize long term SWE manual measurements of a hundred of snow courses within the French Alps. EDF have been operating an automatic SWE sensors network, complementary to historical snow course network. Based on numerous SWE observations time-series and snow modelization (Garavaglia et al., 2017), continuous daily historical SWE time-series have been reconstructed within the 1950-2018 period. These reconstructions have been extented to 1900 using 20 CR (20th century reanalyses by NOAA) reanalyses (ANATEM method, Kuentz et al., 2015) and up to 2100 using GIEC Climate Change scenarii (+4.5 W/m² and + 8.5 W/m² hypotheses). In the scope of this study, Mercantour Natural Parc is particularly interested by snow scenarii in the future and its impacts on their local flora and fauna.

Considering observations within Durance watershed and Mercantour region, this communication focuses on: (1) long term (1900-2018) analyses of variability and trend of hydrometeorological and snow variables (total precipitation, air temperature, snow water equivalent, snow line altitude, snow season length, streamflow regimes) , (2) long term variability of snow and hydrological regime of snow dominated watersheds and (3) future trends (2020 -2100) using GIEC Climate Change scenarii.

Comparing old period (1950-1984) to recent period (1984-2018), quantitative results within these regions roughly shows an increase of air temperature by 1.2 °C, an increase of snow line height by 200m, a reduction of SWE by 200 mm/year and a reduction of snow season duration by 15 days. Characterization of the increase of snow line height and SWE reduction are particularly important at a local and watershed scale. Then, this communication focuses on impacts on long-term time scales (2050, 2100). This long term change of snow dynamics within moutainuous regions both impacts (1) water resources management, (2) snow resorts and artificial snow production developments or (3) ecosystems dynamics.Connected to the evolution of snow seasonality, the impacts on hydrological regime and some streamflow signatures allow to characterize the possible evolution of water resources in this mediteranean and moutianuous region This study allowed to provide some local quantitative scenarii.

How to cite: Mathevet, T., Thébault, C., Mansons, J., Le Lay, M., Valery, A., Brenot, A., and Gailhard, J.: Long-term (1900-2100) Hydrometeorological and Snow Water Equivalent reconstructions in the French Southern Alps (Mercantour Natural Parc)., EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-15872,, 2021.