Alessandro Dell'Aquila

Delivering validated climate services for resilient European Seas on a decadal to multi-decadal horizon is a challenge. The recently started HEU RIVIERADE project brings together the scientific communities geared into CORDEX and the Copernicus Marine Service and capitalizes on their unique scientific experience to develop and implement a pre-operational and replicable multi-model framework and protocols to produce, downscale, assess and deliver state-of-the-art decadal predictions and multi-decadal projections of climate change and related impacts on marine ecosystems, covering the basin scale and the coastal areas, up to, and including, development and demonstration of climate services.RIVIERADE will target three European Seas (Baltic, Black, Mediterranean), to produce data and information for ocean health, sustainable blue economy, and coastal climate risks, downstreaming the data flow from climate ensembles to coastal areas at different spatial resolutions and for selected areas, in a circular process based on users and stakeholders engagement, co-design and assessment of innovative climate services.The RIVIERADE process of co-design and co-development of regional ocean climate impact/risk services and of regional ocean climate services supporting blue economy will be carried out through engagement of stakeholders and perspective users, in order to foster a continuous interaction between end-users and scientists to identify and prioritise societal needs.We present the methodological charter adopted to codesign and test the RIVIERADE climate services demonstrators. The interaction with stakeholders and end-users firstly includes the setting-up of an Users and Stakeholders Advisory Board (USAB) since the beginning of the activities. USAB will be composed by sectoral coordinating organizations (e.g., territorial decision-makers, regional environmental commissions, national technology clusters, research institutions) who have already expressed interest in joining us or belong to collaboration networks already established by the project partnership. Starting from the prioritised contacts identified by the umbrella organizations present in USAB, a representative sample of specific end-users will be identified and engaged to co-design and co-develop demonstrators for the three regional seas. Scoping workshops will be organised at the early stage of the project to present the innovative tools that will be developed in RIVIERADE, to identify and prioritise the specific needs of users involved in terms of data, information and knowledge required, as well as related spatial and temporal scales. A relevant expected outcome of the USAB workshops will be to build a common terminology, to be adopted in the project and beyond, between users and providers of services to smooth the overall co-design process and the following activities of testing and validation of the services. Subsequently, the effectiveness of the demonstrators will be assessed by analysing their support on critical decisions focusing on critical years/events selected by the users. Finally, the value of demonstrators in supporting decision-making processes for early adopters will be showcased also considering potential enablers and barriers in each case study. Factors influencing the value of a service to the end-user, will be discussed with users in a large showcasing event where the final version of the tools will be presented.

We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for the assessment of climate change signals, with a focus on precipitation extreme events. We performed hindcast (i.e., ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980–2014) and future (2015–2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, a double-nesting approach is adopted to dynamically downscale global data to the regional domain of interest, firstly over the Europe (EURO) COordinated Regional climate Downscaling Experiment (CORDEX) domain, at a spatial resolution of 15 km, and then further refined (second nesting) over Italy and the northwestern Mediterranean at a resolution of 5 km, i.e., in the so-called gray zone (5–10 km), close to the convection-permitting (CP) limit. Besides validating the experimental protocol, this work potentially questions the need for climate simulations to always resort to deep convection parameterizations when spatial refinement is increased up to the limit of the CP scale, yet convective processes are still not explicitly resolved. Analyses of air temperature and precipitation are presented, with a focus on the spatial distribution of precipitation, its probability density function, and the statistics of extreme events for both current climate and far-end scenarios. By the end of the century for all the scenarios and seasons there is a projected general warming along with an intensification of the hydrological cycle over most of continental Europe and mean precipitation reduction over the Mediterranean region accompanied, over the Italian Peninsula, by a strong increase in the intensity of extreme precipitation events, particularly relevant for the SSP5-8.5 scenario during autumn.

We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for the assessment of climate change signals, with a focus on precipitation extreme events. We performed hindcast (i.e. ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980–2014) and future (2015–2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, a double nesting approach is adopted to dynamically downscale global data to the regional domain of interest, firstly over the Europe (EURO) CORDEX domain, at a spatial resolution of 15 km, and then further refined (second nesting) over Italy and north-western Mediterranean, at a resolution of 5 km, i.e. in the so-called gray-zone (5–10 km), close to the convection permitting (CP) limit. Besides validating the experimental protocol, this work potentially questions the need for climate simulations to always resort to deep-convection parameterizations when spatial refinement is increased up to the limit of the CP scale, yet convective processes are still not explicitly resolved. Analyses of the most relevant Essential Climate Variables (ECVs) are presented, with a focus on the spatial distribution of precipitation, its probability density function, and the statistics of extreme events, for both current climate and far-end scenarios. By the end of the century for all the scenarios and seasons there is a projected general warming along with an intensification of the hydrological cycle over most of the continental EU and mean precipitation reduction over the Mediterranean region accompanied, over Italian Peninsula, by a strong increase in the intensity of extreme precipitation events, particularly relevant for the SSP5-8.5 scenario during autumn.

We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for the assessment of climate change signals, with a focus on precipitation extreme events. We performed hindcast (i.e. ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980–2014) and future (2015–2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, a double nesting approach is adopted to dynamically downscale global data to the regional domain of interest, firstly over the Europe (EURO) CORDEX domain, at a spatial resolution of 15 km, and then further refined (second nesting) over Italy and north-western Mediterranean, at a resolution of 5 km, i.e. in the so-called gray-zone (5–10 km), close to the convection permitting (CP) limit. Besides validating the experimental protocol, this work potentially questions the need for climate simulations to always resort to deep-convection parameterizations when spatial refinement is increased up to the limit of the CP scale, yet convective processes are still not explicitly resolved. Analyses of the most relevant Essential Climate Variables (ECVs) are presented, with a focus on the spatial distribution of precipitation, its probability density function, and the statistics of extreme events, for both current climate and far-end scenarios. By the end of the century for all the scenarios and seasons there is a projected general warming along with an intensification of the hydrological cycle over most of the continental EU and mean precipitation reduction over the Mediterranean region accompanied, over Italian Peninsula, by a strong increase in the intensity of extreme precipitation events, particularly relevant for the SSP5-8.5 scenario during autumn.

We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for the assessment of climate change signals, with a focus on precipitation extreme events. We performed hindcast (i.e. ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980–2014) and future (2015–2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, a double nesting approach is adopted to dynamically downscale global data to the regional domain of interest, firstly over the Europe (EURO) CORDEX domain, at a spatial resolution of 15 km, and then further refined (second nesting) over Italy and north-western Mediterranean, at a resolution of 5 km, i.e. in the so-called gray-zone (5–10 km), close to the convection permitting (CP) limit. Besides validating the experimental protocol, this work potentially questions the need for climate simulations to always resort to deep-convection parameterizations when spatial refinement is increased up to the limit of the CP scale, yet convective processes are still not explicitly resolved. Analyses of the most relevant Essential Climate Variables (ECVs) are presented, with a focus on the spatial distribution of precipitation, its probability density function, and the statistics of extreme events, for both current climate and far-end scenarios. By the end of the century for all the scenarios and seasons there is a projected general warming along with an intensification of the hydrological cycle over most of the continental EU and mean precipitation reduction over the Mediterranean region accompanied, over Italian Peninsula, by a strong increase in the intensity of extreme precipitation events, particularly relevant for the SSP5-8.5 scenario during autumn.

Similarly to weather forecasting techniques, climate projections also aim to achieve very high spatial and temporal resolutions, which are needed both as inputs to impact models and to perform reliable risk assessment studies. This is all the more true for the Mediterranean region and the Italian territory in particular, whose heterogeneous and complex morphology do affect the local climate (highly sensitive to global warming), making this area particularly vulnerable to hydrogeological risks, such as heavy rainfall, landslides and flooding with serious losses of both human lives and economic. We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for assessing climate change signals, with a particular focus on small-scale phenomena and extreme events. We performed hindcast (i.e. ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980-2014) and future (2014-2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, we used a double nesting approach to downscale global data first to a regional domain, covering the whole of Europe (EURO-CORDEX domain) with a spatial resolution of 15 km, and subsequently to a fine spatial scale domain centered over Italy and the north-western Mediterranean with a resolution of 5 km, (i.e. close to the convection permitting limit resolution). We explore the effects of pushing the resolution to km-scale while still falling within the so-called “gray zone” (5-10 km), where deep convection can still be insufficiently resolved and a parameterization of the deep convection is still needed to fully represent it. We present the analysis of the most relevant Essential Climate Variables (ECVs), and the statistics of extreme events for both the current climate and for end of the century scenarios. Results highlight that the gray-zone model in the configuration here implemented mimics the behavior of a convection permitting model and improves the representation of the mean precipitation field over the entire domain. This improvement is also detectable for heavy precipitation, represented through high percentile of daily precipitation (p95 – p99). We show the multi-scenario projection of the climate signal for both the simulations on the common domain.This study was carried out within: RETURN Extended Partnership and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.3 – D.D. 1243 2/8/2022, PE0000005);ICSC Italian Research Center on High-Performance Computing, Big Data and Quantum Computing and received funding from the European Union Next-GenerationEU (National Recovery and Resilience Plan – NRRP, Mission 4, Component 2, Investment 1.4 – D.D: 3138 16/12/2021, CN00000013)

In 2024,the year with the warmest global temperature since 1850 (Copernicus Climate Change Service), very high temperatures were observed at regional scale.In the Mediterranean Sea,the measured sea temperature locally displayed values that were never recorded before. Satellite and in situ observationsindicate that during 2024 the Mediterranean Sea has experienced a sequence of strong marine heat waves, occurring in the months of February, April, June, and August. Thesurface temperature anomalies with respect to the 1990-2020 climatology reached about 3° C in the Algerian and Levantine basins in February, and 4-5° C in the northern part of the western Mediterranean and in the Adriatic Sea in August. Moreover, in situ observations incoastal areas oftheTyrrhenian Sea, gathered through aCitizen Scienceactivity (MEDFEVER initiative), indicated strong warming even on the seafloor, as a result of rapid heat transfer from the sea surface to the bottom. Satellite data show that surface temperature anomalies were strongly modulated by large gyres and eddies. We find that these dynamical structures control the anomalous warming induced by air-sea interactionsin regions such as the Algerian Basin, the Tyrrhenian Sea, and the Levantine basin. Estimates of mean and eddy kinetic energy from altimeter data suggest that mesoscale structures were particularly energetic during 2024 and favored warming in regions where eddy activity was intense. Model data show that themain quasi-permanent anticyclonic structures throught the basin were very effective in transferringsurface heat anomalies into the deep layers. Finally, we analyze the 2024 Mediterranean summer temperature anomaliesin relationto local and global patterns of atmospheric circulation.

The increasing availability of reliable climate-change information at the regional scales is prompting an ever-growing demand for impact and risk indicators suitable for policy planning and implementation. As highlighted in IPCC AR6, the latter also benefit from the recent advances in attribution and sectoral vulnerability studies, which now enable to identify the most relevant climatic variables and to investigate their past and future trends, characterizing the response of both environmental and socio-economic systems to climate-induced stress. Climate services aim to complement and combine up-to-date scientific knowledge and bottom-up contributions, including stakeholder needs, interests and expectations, to deliver user-oriented information and enhance awareness, preparedness, risk reduction and recovery strategies. Recognizing that climate-proofing our societies cannot be further postponed, the IPCC proposed a synergistic “Climatic Impact-Driver (CID) Framework” as a tool to preliminarily foster and feed physical climate science applications whenever specific information is lacking on the context where climate-change-induced phenomena can emerge as hazardous, beneficial, or inconsequential. Within the generic category of “impact-drivers” (e.g., climate change, population growth, viral outbreaks, technological change, social conflict), IPCC AR6 defined CIDS as “physical climate system conditions (e.g., means, events, and extremes) that affect an element of society or ecosystems”, the extent of their impact depending on system tolerance across interacting elements and regions. Despite their being based on characteristics (intensity, frequency, duration, timing, and spatial extent) that solely depend on complex, scale-spanning physical processes, CIDs are designed to represent the perspective of the affected system or sectoral asset and to provide stakeholders with a more exhaustive and purposeful reckoning of changing, potentially threatening climate conditions. Such an approach allows to evaluate potential impacts and to inter-compare regions, helping prioritize adaptation strategies, while maintaining climate information neutrality until more complex, intrinsically local, risk assessments are conducted, hazard and system specific thresholds defined, and decision-making processes brought into being. There is a nearly unanimous scientific consensus that current climate in many regions of the Earth has already changed with respect to the early or mid-20th century and that climate change has already critically altered CID characteristics, shifting the magnitude, frequency, duration, seasonality and spatial extent of their associated impact indices and indicators. In particular, the Mediterranean basin is experiencing significant changes in temperature and precipitation patterns, which can affect vital economic and environmental sectors in the surrounding countries. Here, the need for systematic and inter-comparable assessments of the expected impacts is particularly urgent, and action prioritization calls for progressively zooming analyses across regional and local scales and across multiple hazards, ideally accounting for interactions and superpositions between both CIDs and sectors, as well as for sector tolerance thresholds. In this context, we present temperature and precipitation related CID indicators at the NUTS-1, NUTS-2 and NUTS-3 aggregation levels, derived from new high-resolution (5 km) climate projections over the Italian peninsula, for both present climate and future scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5), as obtained by downscaling the corresponding global ERA5 and MPI-ESM1-2-HR driven CMIP6 experiments.

We present the results of downscaling CMIP6 global climate projections to local scales for the Mediterranean and Italian regions, aiming to produce high-resolution climate information for the assessment of climate change signals, with a focus on precipitation extreme events. We performed hindcast (i.e. ERA5-driven) and historical simulations (driven by the MPI-ESM1-2-HR model) to simulate the present (1980–2014) and future (2015–2100) climate under three different emission scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5). For each experiment, a double nesting approach is adopted to dynamically downscale global data to the regional domain of interest, firstly over the Europe (EURO) CORDEX domain, at a spatial resolution of 15 km, and then further refined (second nesting) over Italy and north-western Mediterranean, at a resolution of 5 km, i.e. in the so-called gray-zone (5–10 km), close to the convection permitting (CP) limit. Besides validating the experimental protocol, this work potentially questions the need for climate simulations to always resort to deep-convection parameterizations when spatial refinement is increased up to the limit of the CP scale, yet convective processes are still not explicitly resolved. Analyses of the most relevant Essential Climate Variables (ECVs) are presented, with a focus on the spatial distribution of precipitation, its probability density function, and the statistics of extreme events, for both current climate and far-end scenarios. By the end of the century for all the scenarios and seasons there is a projected general warming along with an intensification of the hydrological cycle over most of the continental EU and mean precipitation reduction over the Mediterranean region accompanied, over Italian Peninsula, by a strong increase in the intensity of extreme precipitation events, particularly relevant for the SSP5-8.5 scenario during autumn.