INFORMATION SHEET ON FUTURE CLIMATE:
CLIMATE PROJECTIONS FOR THE CIRCE CASE STUDIES
Summary
A set of six coupled Mediterranean Sea-atmosphere CIRCE climate models form the basis of
climate and marine projections for the CIRCE case studies.
► All models indicate consistent warming by the 2050s, which is higher for Tmax than for Tmin, and
for western Mediterranean case studies (Gulf of Valencia, Gulf of Oran) compared to eastern
Mediterranean case studies.
► Precipitation projections are less consistent than for temperature, but a general decline is
indicated for 8 of the 11 case study sites.
► Additional numbers of ‘very hot summer days’ projected for the 2050s range from 15 for the Gulf
of Valencia to 5 for Alexandria.
►
1. CIRCE climate models
As part of the CIRCE project, a set of Global
Climate Model (GCM) and Regional Climate
Model (RCM) simulations has been performed
with the key innovative attribute of including a
realistic representation of the Mediterranean Sea
coupled with the atmosphere. The six coupled
CIRCE models vary by type, spatial resolution
and boundary forcing (Table 1). The spatial
resolution of the Mediterranean Sea ocean
components is between 7 and 12 km, while the
atmospheric component of the two global
models varies between about 50 and 80 km, and
that of the regional models, between 25 and 30
km. All simulations use the IPCC-SRES A1B
emissions scenario and were run for the period
1950-2050. The CIRCE model ensemble has a
cold bias of about 2°C compared with present-
day (1961-90) observations. Changes are
represented as the difference between the future
30-year period (2021-2050) and the baseline 30year period (1961-90). The models indicate
consistent warming over the entire region which
is strongest in summer (+1.2°C to +2.5°C) and
weakest in winter. The direction of change
averaged over the entire Mediterranean area is
inconsistent for precipitation, with a summer
increase for four models, and a summer decrease
for two models. Climate and marine indicators
have been constructed for each of the coastal and
rural regions using the average of land-based
model grid boxes, and for the urban case studies
using the nearest land-based grid box (checking
for neighbouring inconsistencies).
Table 1: Summary description of the CIRCE models. Temperature (T) changes (°C) and Precipitation (P)
changes (mm per season) for winter (djf) and summer (jja) are averages for all model land and sea grid
boxes over the Mediterranean region
Model
acronym
Type of model, spatial resolution of the
atmospheric component and boundary forcing
CNRM
Stretched grid global model zooming to 50 km over
the Mediterranean area
Global model: ~80 km
INGV
IPSL1
(IPSLreg)
IPSL2
(IPSLglo)
ENEA
MPI
LMDZ regional model: 30 km. Forcing from an
earlier (non-CIRCE) IPSL GCM run
Coupled LMDZ global and LMDZ regional model:
30 km
Regional model: 30 km, forcing from the CIRCE
INGV model.
Regional model, 25 km, forcing from an ECHAM5
GCM (non-CIRCE) run
Seasonal mean response over the
Mediterranean for 2021-2050 with
respect to 1961-1990
Tdjf
Tjja
Pdjf
Pjja
0.78
1.42
-3
-3
1.44
1.68
-23
-8
2.01
2.46
-10
-5
1.00
1.16
+6
-6
0.97
1.41
-15
+6
1.38
1.52
-3
+1
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Case study projections: mean temperature
Projected temperature changes are slightly larger for case studies located in the western (Gulf of
Valencia and Gulf of Oran) and central (Tuscany and Puglia) Mediterranean than in the eastern
Mediterranean (Figure 1). Changes in mean Tmax (maximum temperature) tend to be larger than
changes in Tmin (minimum temperature), particularly in the western Mediterranean. The largest
ensemble-mean change is for Tmax in the Gulf of Oran almost 2°C). The IPSL1 model system
consistently indicates the greatest warming, while the ENEA (regional) and CNRM (stretched grid)
models tend to give the least warming.
Figure 1: Histograms of (top) annual Tmax (°C) and (bottom) Tmin (°C) changes (2021-2050 minus 19611990) based on CIRCE model data for the urban, rural and coastal case studies. The ensemble-mean change is
shown (bars), together with changes for the five individual models. IPSL= IPSL1/IPSLreg.
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Case study projections: temperature extremes
A selected number of climate extremes were selected as case-study specific indicators. For example,
projected changes in the number of ‘very hot summer days’ (Tx95n) are shown for all case studies in
Figure 2. The spatial pattern in the simulated future response is similar to Tmax being largest for the
western case study of the Gulf of Valencia (ensemble mean of about 13 more ‘very hot days’ per
summer) and least for the south-eastern case study of Alexandria (ensemble mean of about 5 more
‘very hot days’ per summer). There is a large model spread in the response: the IPSL1 model generally
projects the greatest increase (more than 25 additional days for the Gulf of Valencia and Tuscany)
while the least increase is generally for the MPI model (less than five days).
Figure 2: Histograms of changes (2021-2050 minus 1961-1990) in the number of very hot summer days
(Tx95n) based on CIRCE model data for the urban, rural and coastal case studies. The ensemble-mean change
is shown (bars), together with changes for the five individual models. IPSL= IPSL1/IPSLreg.
Other temperature extremes considered (not shown) include very hot nights for the urban case studies,
which show the largest increase for Athens and for the summer season. Additional regional climate
model sensitivity studies undertaken for the CIRCE urban case studies suggest that these results
underestimate the frequency of extreme temperature events due to the exclusion of urban heat island
effects.
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Case study projections: precipitation
Total annual and extended winter season (October to March) precipitation were also selected as
climate indicators (Figure 3). The ensemble mean suggests a decline in precipitation totals for all case
studies except for Alexandria and the West Nile Delta and little change in the Judean Foothills. There
is less spatial or inter-model consistency in precipitation projections than for temperature.
Figure 3: Histograms of changes (in mm for 2021-2050 minus 1961-1990) in (a) annual and (b) extended
winter (October to March) total precipitation based on CIRCE model data for the urban, rural and coastal
case studies. The ensemble-mean change is shown (bars), together with changes for the five individual
models IPSL= IPSL1/IPSLreg.
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Marine conditions
Sea surface temperature (SST)
The CIRCE models show an ensemble-mean cold
bias (of about 2°C) relative to the observation
period, 1961-90. Projections for the future period
2021-2050 consistently indicate a warming of SST
(with values ranging from +0.8 °C to 1.8°C
compared to the period 1961-1990).
Sea surface salinity (SSS)
SSS is also underestimated by the CIRCE ensemble
(by about -0.4 psu for the period 1961-1990).
Models suggest an increase in Atlantic freshwater
input through the Straits of Gibraltar. Consequently,
projected SSS show a generally negative trend, but
the model spread is large, from +0.05 to -0.35 psu.
Sea level change
Changes in Mediterranean sea level are assessed
through the steric effect [due to volume change –
the largest component of sea level change (roughly
70% of total)]. Models suggest an increasing trend
in sea level, with values reaching +10 cm in 20212050 and nearly +14 cm in 2050 (all relative to the
period 1961-1990).
Acknowledgements
CIRCE (Climate Change and Impact Research: the Mediterranean Environment) is funded by the Commission of the
European Union (Contract No 036961 GOCE) http://www.circeproject.eu/. This information sheet forms part of the
CIRCE deliverables D11.3.6, D11.4.5, and D11.5.7. The CIRCE model data were provided by INGV-CMCC (Silvio
Gualdi, Enrico Scoccimarro); MF (Florence Sevault, Clotilde Dubois); IPSL-CNRS (Laurent Li); ENEA (Alessandro
Dell'Aquila, Adriana Carillo); and MPIM-HH (Alberto Elizalde Arellano). For assistance in processing model data,
thanks are extended to Dimitra Founda, Effie Kostopoulou, Basil Psiloglou, Kostas Varotsos (NOA), Gillian Kay (UK
Meteorological Office), Dimitrios Efthymiadis and Richard Cornes (UEA).
References
► Gualdi S., Somot S., May W., Castellari S., Déqué M., Adani M., Artale V., Bellucci A., Breitgand J.S., Carillo A.,
Cornes R., Dell’Aquilla A., Dubois C., Efthymiadis D., Elizalde A., Gimeno L., Goodess C.M., Harzallah A.,
Krichak S.O., Kuglitsch F.G., Leckebusch G.C., L’Heveder B.P., Li L., Lionello P., Luterbacher J., Mariotti A.,
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U., and Xoplaki E. 2011. Future Climate Projections. In Regional Assessment of Climate Change in the
Mediterranean: A. Navarra, L.Tubiana (eds.), Springer, Dordrecht, The Netherlands.
► Goodess C.M., Agnew M.D., Giannakopoulos C., Hemming D., Bindi M., Bradai M. N., Congedi L., Dibari C., ElAskary H., El-Raey M., Ferrise R., Founda D., Grünzweig J., Harzallah A., Hatzaki M., Kay G., Kostopoulou E.,
Lionello P., Mösso C., Oweis T., Psiloglou B., Reale M., Salem S. B., Sanchez-Arcilla A., Senouci M., Tanzarella
A. and Varotsos K. 2011. Integration of the climate impact assessments with future projections. In Regional
Assessment of Climate Change in the Mediterranean: A. Navarra, L. Tubiana (Eds.), Springer, Dordrecht, The
Netherlands.
Authors: Clare Goodess1 (c.goodess@uea.ac.uk), Christos Giannakopolous2 (cgiannak@meteo.noa.gr), Maria Hatzaki2
(marhat@phys.uoa.gr), Maureen Agnew1 (m.agnew@uea.ac.uk)
1
Climatic Research Unit, School of Environmental Sciences, University of East Anglia, Norwich, UK
Institute for Environmental Research and Sustainable Development, National Observatory of Athens, V. Pavlou and
Metaxa Str., P. Pendeli, GR-15236 Athens, Greece
2
Date: May 2011; Updated July 2011
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