P. Mercogliano, 30 Novembre - 1 Dicembre 2021 - Webinar: I cambiamenti climatici: sfide ed aspetti evolutivi dei sistemi statistici Titolo: Assessing climate change with climate models: gaps and perspectives

1. Assessing climate change
with climate models: gaps
and perspectives
Paola Mercogliano
Head of the Research Division REMHI (Regional Model and geo-
hydrological Risk)
Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici
30.11-1.12//2021

2. ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
Climate change a global phenomenon
2
IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis.
Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on
Climate. Cambridge University Press. In Press.
Climate change is a global
phenomenon, but it manifests
itself differently in the different
geographical regions.
Also impacts are very different and they are generally
experienced on a local, national and regional scale,
which are also the scales on which decisions are
generally made.
Reliable information on climate change are therefore
urgent on regional and local scales to provide detailed
impact and risk assessments

3. Climate models: a tool describing evolution of the climate system
3
Numerical climate models thanks to a
set of mathematical equation
representing the physical laws
describing the evolution of climate
system permits us to understand and
possibly predict the evolution of the
climate system
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO

4. Climate models and climate changes
Scientists starts from applying climate models over the past periods and then thanks to the evaluation on
their performances compared with observations on representing the different climate features of interest.
The models simulate the physics, chemistry and biology of the atmosphere, land and oceans in great detail,
and require some of the largest supercomputers in the world to generate their climate projections.
Past to present days Near and Mid future to the
End of the century
Long time series of in-situ
observations and satellite variables, and
reanalysis
Regional and global climate projections
Source:
https://www.ecmwf.int/en/ab
out/media-centre/science-
blog/2017/era5-new-
reanalysis-weather-and-
climate-data
Source: Giorgi, F. (2019).
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
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5. 5
Different models for different goals
General circulation models are the most
advanced tools currently available to simulate
the response of the global climate system to
rising greenhouse gas concentrations.
GCMs ensure physical coherence between
variables but there are important differences
between the real world and its model
representation due to the current low spatial
resolution required to simulate climate and
climate change across the Earth.
Small-scale effects (such as ones related to
topography) that are relevant to define local
climate are still poorly represented in a GCM.
GCMs are not adequate to support regional
impact studies and adaptation strategies.
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO

6. 6
How is a local climate scenario built?
SRES/RCP Scenarios (GHG scenarios)
Earth System
Models/GCM
Regional Climate
Models
Very high resolution
Regional Climate
Models
In order to simulate the characteristics of the climate on
a LOCAL SCALE, more detail is required. For this
purpose regional models have been created, which
simulate the climate of a limited part of the Earth.
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO

7. 7
RCMs from EURO-CORDEX Program
Currently, the climate models used are subject to uncertainties.
Following Collins (2007), these uncertainties can be divided into 3
components:
1) The uncertainty due to the normal variability of the atmosphere
2) The uncertainty present in GHG scenarios
3) The uncertainty due to the imperfect simulation, by the
models, of the climate system
In order to manage this last point (at least to quantify the
uncertainty), there are some projects in Europe, such as the
CORDEX initiative, which have the aim, in a coordinated way
(e.g. same domain, same horizontal resolution), provide the so-
called “multi-model ensembles”.
EURO-CORDEX European branch of the CORDEX program,
sponsored by the World Climate Research Program (WRCP) with the
aim of producing projections using regional climate models in
different areas of the globe.
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO

8. RCP2.6
RCP4.5 RCP8.5
2021-2050
vs
1981-2010
2041-2070
vs
1981-2010
Expected variation for Mean Temperature over Italy
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
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9. RCP2.6 RCP4.5 RCP8.5
2021-2050
vs
1981-2010
2041-2070
vs
1981-2010
Expected variation for Annual precipitation over Italy
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
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10. 10
RCMs from CMCC Foundation
Reduction of uncertainty due to the imperfect simulation of
the climate system
MAE
COSMO-
CLM
MAE ensemble
mean CORDEX
Errore COSMO-
errore ensemble
mean CORDEX
EOBS
Tmean [°C] 2.1 2 0.1
R20 [giorni/anno] 5 6 -1
FD [giorni/anno] 18 24 -6
SU95p giorni/anno] 10 14 -4
Winter Precipitation [mm] 79 99 -20
Summer Precipitation [mm] 50 87 -37
EURO4M
R20 5 6 -1
Winter Precipitation [mm] 89 105 -16
Summer Precipitation [mm] 76 103 -27
The REMHI division @ CMCC has published, starting from 2015, high-resolution climate
projections on Italy. Data are currently largely used in Italy for climate analysis and to define
adaptation strategies and risk evaluation
E. Bucchignani, M. Montesarchio, A.L. Zollo, P. Mercogliano, High resolution climate simulations with COSMO-CLM over Italy: performance evaluation and climate
projections for the 21st century, International Journal of Climatology, 2015, DOI: 10.1002/joc.4379
A. L. Zollo, V. Rillo, E. Bucchignani, M. Montesarchio, P. Mercogliano, Extreme temperature and precipitation events over Italy: assessment of high resolution simulations
with COSMO-CLM and future scenarios, International Journal of Climatology, 2015. DOI: 10.1002/joc.4401
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO

11. The best configuration to represent Italian climate features was identified thanks to a sensitivity analysis.
In this analysis, the evaluation was carried out with respect to different datasets:
1) E-OBS gridded dataset for temperature and precipitation (0.25, about 28 km)
2) the EURO4M - APGM dataset for precipitation (about 5 km)
3) High resolution data provided by regional ARPAs for temperature and precipitation.
(a) Veneto, Tuscany, Sardinia, Campania and
Calabria precipitation,
(b) gridded Po Valley temperature and precipitation,
(c) gridded EURO4M precipitation and
(d) gridded Piedmont precipitation. a
c
c
d
The relevance of using high – resolution in situ dataset to define RCMs
One of the main gaps in the development of very detailed
models is the availability of long, high-resolution quality
series of observations.
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12. Source :“Do Convection-Permitting Regional Climate Models Improve
Projections of Future Precipitation Change? in: Bulletin of the American
Meteorological SocietyVolume 98 Issue 1 (2017) (ametsoc.org)”
CLIMATE MODEL: FROM GLOBAL TO URBAN AND LOCAL SCALE
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
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13. CLIMATE CHANGE IMPACTS on URBAN AREAS: HEAT WAVES
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
Urban Heat Island=DTU-R=TUrban-TRural
hiips://www.cmcc.it/it/rischio -clima-citta-2021#download
hiips://www.campusvarta.com/campus -
updates/educational-institutions-need-to-step-out-
to-address-the-issue-of-urban-heat-island/
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14. Evaluation of climate change risks is an important
components of local adaptation decision-making
hiips://climate.copernicus.eu/pluvial -flood-risk-assessment-urban-areas
CLIMATE CHANGE IMPACTS on URBAN AREAS: FLOOD
ASSESSING CLIMATE CHANGE WITH CLIMATE MODELS: GAPS AND PERSPECTIVES | PAOLA MERCOGLIANO
Pluvial flood risk analysis based on 2 km
reanalysis by REMHI over different 20
European cities showing the added value of
CPM for urban impact analysis
hiips://www.youtube.com/watch?v=_xk3 -Luiimw
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15. grazie
Paola Mercogliano
Responsabile della Divisione di Ricerca REMHI | Fondazione CMCC
Paola.mercogliano@cmcc.it
per l’attenzione