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The average PM10 daily levels over the urban area of Thessaloniki, Greece, usually exceed the air quality limits and therefore the improved PM chemical composition and air quality modeling results that will facilitate the design of the most appropriate mitigation measures (e.g., limitations in wood combustion for heating purposes) are essential. The air quality modeling system WRF-CAMx was applied over a 2 × 2 km2 horizontal resolution grid covering the greater area of Thessaloniki for the year 2015, when Greece was still confronting the consequences of the financial crisis. The output hourly surface concentrations of twelve PM species at three sites of different environmental type characterization in the city of Thessaloniki were temporally and spatially analyzed. Carbonaceous aerosols (organic and elemental) are the major contributor to total PM10 levels during winter representing a 35–40% share. During summer, mineral aerosols (excluding dust) distribute by up to 48% to total PM10 levels, being the major contributor attributed to road traffic. PM species, during winter, increase in the morning and in the afternoon mainly due to road transport and residential heating, respectively, in addition with the unfavorable meteorological conditions. An underestimation of the primary organic carbon aerosol levels during winter is identified. The application of the modeling system using a different speciation profile for the fine particles emissions from residential heating based on observational data instead of the CAMS emissions profile revealed an improvement in the simulated OC/EC values for which a 50% increase was identified compared to the base run.

The rise of surface temperature due to climate change has a significant impact on the growth of different plant species, including aromatic plants, agricultural crops, fruit trees, and forests. Within the framework of the MICROSERVICES project, that aims on improving the capacity to predict the cascading effects of climate change on microbial diversity, crop-microbiome interactions and agricultural ecosystem functions, we studied the future projection of agro-climatic zones over Europe under two different IPCC Representative Concentration Pathways (RCP4.5 and RCP8.5). To this end, an ensemble of 11 bias-corrected EURO-CORDEX simulations covering the period 1981-2100 was used following the methodology of Ceglar et al. (2019)*. The agro-climatic zones were identified based on two temperature-related parameters, the Growing Season Length (GSL) and the Active Temperature Sum (ATS). The categorization into one of the 8 agro-climatic zones was implemented by applying the k-means clustering method for the reference period 1981-2010. Then, the agro-climatic zone patterns over Europe for the intermediate period 2031-2060 and the end-of-the-century period 2071-2100 were compared against that of the reference period. Our results point towards a strong northward shift of the agroclimatic zones, especially under the no-mitigation emission scenario (RCP8.5) at the end of the century. For the moderate mitigation scenario (RCP4.5), a significant shift of the agroclimatic zones is also observed for the intermediate and the end-of-the-century periods for extended areas in Europe. Our results are in line with that of Ceglar et al. (2019), who studied the migration of agro-climatic zones over Europe under the 2 oC warming level utilizing a subset of the simulations used in this study. *Ceglar et al., Earth's Future, 7, 1088-1101, https://doi.org/10.1029/2019EF001178, 2019.This research was supported by the MICROSERVICES project funded by the General Secretariat for Research and Innovation (GSRI, Greece) under the Action ERANETs 2021A [Call ID: 037KE - A/A MIS 4888] (Project Number: T12ERA5-00075) and through the 2019-2020 BiodivERsA joint call for research proposals [BiodivClim ERA-Net COFUND programme].

Long-term exposure to ambient ozone is linked with respiratory-related mortality, while the emerging climate change is projected to pose double-edged challenges for ozone air quality. Here, we calculate the impact of emissions- and climate-change under SSP3-7.0 scenario on ozone-related mortality on a global scale, using historical (experiment histSST) and future simulations (experiments ssp370SST and ssp370pdSST) from three CMIP6 Earth System Models (ESMs) (GFDL-ESM4, EC-Earth3-AerChem, and UKESM1-0-LL). The ssp370SST experiment follows time-varying SSTs, while the SSP370pdSST follows a present-day climatology for SSTs. The chronic obstructive pulmonary disease mortality attributable to ozone pollution is estimated following the Global Burden Disease (GBD) 2019 approach, by using the ozone season daily maximum 8-hour mixing ratio (OSDMA8), the baseline mortality rate (from the GBD), and the SSP3-7.0 present and future gridded population. An increase in ozone-related mortality of approximately 2.5 million people per year globally is projected at the end of the century (2090) with respect to 2000 due to emissions and population changes. The climate-change footprint on ozone-related mortality exhibits large variability among the ESMs; yet, over India and China all ESMs project an increase of ozone-related mortality in the future, highlighting the importance of the ozone penalty due to global warming in regions with strong anthropogenic sources.

This study presents an updated assessment of the projected climate change over Greece in the near future (2021–2050) and at the end of the 21st century (2071–2100) (EOC), relative to the reference period 1971–2000, and focusing on seasonal crop-specific climatic indices. The indices include days (d) with: a maximum daily near-surface temperature (TASMAX) > 30 °C in Spring, a TASMAX > 35 °C in Summer (hot days), a minimum daily near-surface temperature (TASMIN) < 0 °C (frost days) in Spring, a TASMIN > 20 °C (tropical nights) in Spring–Summer and the daily precipitation (PR) > 1 mm (wet days) in Spring and Summer covering the critical periods in which wheat, tomatoes, cotton, potato, grapes, rice and olive are more sensitive to water and/or temperature stress. The analysis is based on an ensemble of 11 EURO-CORDEX regional climate model simulations under the influence of a strong, a moderate, and a no mitigation Representative Concentration Pathway (RCP2.6, RCP4.5 and RCP8.5, respectively). The indices related to TASMAX are expected to increase by up to 11 days in Spring and 40 days in Summer, tropical nights to rise by up to 50 days, frost days to decrease by up to 20 days, and wet days to decline by up to 9 days in Spring and Summer, at the EOC with an RCP8.5. The increased heat stress and water deficit are expected to have negative crop impacts, in contrast to the positive effects anticipated by the decrease in frost days. This study constitutes a further step towards identifying the commodities and/or regions in Greece which, under climate change, are or will be significantly impacted.

Tropopause folds are the key process underlying stratosphere-to-troposphere transport (STT) of ozone, and thus they affect tropospheric ozone levels and variability. In the present study we perform a process-oriented evaluation of Copernicus Atmosphere Monitoring Service (CAMS) reanalysis (CAMSRA) O3 during folding events over Europe and for the time period from 2003 to 2018. A 3-D labeling algorithm is applied to detect tropopause folds in CAMSRA, while ozonesonde data from WOUDC (World Ozone and Ultraviolet Radiation Data Centre) and aircraft measurements from IAGOS (In-service Aircraft for a Global Observing System) are used for CAMSRA O3 evaluation. The profiles of observed and CAMSRA O3 concentrations indicate that CAMSRA reproduces the observed O3 increases in the troposphere during the examined folding events. Nevertheless, at most of the examined sites, CAMSRA overestimates the observed O3 concentrations, mostly at the upper portion of the observed increases, with a median fractional gross error (FGE) among the examined sites >0.2 above 400 hPa. The use of a control run without data assimilation reveals that the aforementioned overestimation of CAMSRA O3 arises from the data assimilation implementation. Overall, although data assimilation assists CAMSRA O3 to follow the observed O3 enhancements in the troposphere during the STT events, it introduces biases in the upper troposphere resulting in no clear quantitative improvement compared to the control run without data assimilation. Less biased assimilated O3 products, with finer vertical resolution in the troposphere, in addition to higher IFS (Integrated Forecasting System) vertical resolution, are expected to provide a better representation of O3 variability during tropopause folds.

It is presented an analysis of the effect of climate change on surface ozone (O3) discussing the related penalties and benefits around the globe from the global modeling perspective based on simulations with five CMIP6 (Coupled Model Intercomparison Project Phase 6) Earth System Models. All models conducted simulation experiments considering future climate (ssp370SST) and present-day climate (ssp370pdSST) under the same future emissions scenario (SSP3-7.0). Over regions remote from pollution sources, there is a robust decline in mean surface ozone concentration varying spatially from -0.2 to -2 ppbv oC-1, with strongest decline over tropical oceanic regions, which is mainly linked to the dominating role of enhanced ozone chemical loss with higher water vapour abudances under a warmer climate. However, ozone increases over regions close to anthropogenic pollution sources or close to enhanced natural Biogenic Volatile Organic Compounds (BVOC) emission sources with a rate ranging regionally from 0.2 to 2 ppbv oC-1, implying a regional surface ozone penalty due to global warming. The individual models show this robustly for south-eastern China and India as well as for regions of Africa but there are inter-model differences in areas within Europe and the United States (US) as well as in South America. The future climate change enhances the efficiency of precursor emissions to generate surface ozone in polluted regions and thus the magnitude of this effect depends on the regional emission changes considered in this study within the SSP3_7.0 scenario. The comparison of the climate change impact effect on surface ozone versus the combined effect of climate and emission changes indicates the dominant role of precursor emission changes in projecting surface ozone concentrations under future climate change scenarios. The authors from Aristotle University of Thessaloniki acknowledge funding from the Action titled "National Νetwork on Climate Change and its Impacts - CLIMPACT" which is implemented under the sub-project 3 of the project "Infrastructure of national research networks in the fields of Precision Medicine, Quantum Technology and Climate Change", funded by the Public Investment Program of Greece, General Secretary of Research and Technology/Ministry of Development and Investments.

Here, we present an updated assessment of projected climate change over Greece in the near future and at the end of the 21st century. The analysis is based on an ensemble of 11 high-resolution EURO-CORDEX simulations based on historical emission data and three different greenhouse gas concentration scenarios, namely, RCP2.6, RCP4.5, and RCP8.5. Our results strongly point towards a warmer future under all the examined RCPs. Under the extreme RCP8.5 scenario, temperature is expected to increase on average by 1.6 oC (12%) in the near future and 4.3 oC (33%) at the end of the century. The number of hot days and tropical nights per year is expected to increase significantly and the number of frost days to decrease. Also, the future will be possibly drier, with statistically robust results for the end-of-the-century period under RCP8.5 only. On average, precipitation is expected to decrease under RCP8.5 by -0.4 mm day-1 (-16%) and the number of consecutive dry days per year to increase by 15.4 days (30%) at the end of the century.The authors acknowledge funding from the Action titled "National Νetwork on Climate Change and its Impacts - CLIMPACT" which is implemented under the sub-project 3 of the project "Infrastructure of national research networks in the fields of Precision Medicine, Quantum Technology and Climate Change", funded by the Public Investment Program of Greece, General Secretary of Research and Technology/Ministry of Development and Investments.

An updated and expanded representation of organics in the chemistry general circulation model EMAC (ECHAM5/MESSy for Atmospheric Chemistry) has been evaluated. First, the comprehensive Mainz Organic Mechanism (MOM) in the submodel MECCA (Module Efficiently Calculating the Chemistry of the Atmosphere) was activated with explicit degradation of organic species up to five carbon atoms and a simplified mechanism for larger molecules. Second, the ORACLE submodel (version 1.0) now considers condensation on aerosols for all organics in the mechanism. Parameterizations for aerosol yields are used only for the lumped species that are not included in the explicit mechanism. The simultaneous usage of MOM and ORACLE allows an efficient estimation of not only the chemical degradation of the simulated volatile organic compounds but also the contribution of organics to the growth and fate of (organic) aerosol, with the complexity of the mechanism largely increased compared to EMAC simulations with more simplified chemistry. The model evaluation presented here reveals that the OH concentration is reproduced well globally, whereas significant biases for observed oxygenated organics are present. We also investigate the general properties of the aerosols and their composition, showing that the more sophisticated and process-oriented secondary aerosol formation does not degrade the good agreement of previous model configurations with observations at the surface, allowing further research in the field of gas–aerosol interactions.