talks
A collection of recent talks
2025
- AGU 2025Terrestrial Atmospheric and Climatological Responses to Recent (within 10 Mya) Encounters with Dense Interstellar CloudsMiller al.2025
Recently, Opher et al. (2024) proposed that the Solar System passed through a dense interstellar cloud called the Local Lynx of Cold Clouds 2-3 million years ago, with another potential crossing 7-8 million years ago. Due to the cloud’s high density and ram pressure, it would have greatly compressed the heliosphere to within Earth’s orbit, exposing Earth directly to the interstellar medium. Prior investigations into these events have used simple models and scaling relations. In this study, we utilize for the first time a state-of-the-art 3D climatological model (CESM/WACCM) to demonstrate the effects of interstellar hydrogen in Earth’s atmosphere. We examine how this source of high-altitude hydrogen modifies the chemistry and dynamics in the stratosphere and mesosphere. In particular, there is a broad depletion of mesospheric ozone and a concomitant decrease in temperature. We also examine other methods of interstellar forcing, such as cosmic rays and interstellar dust. We conclude with a discussion of potential surface effects.
- UPCLIV 2025
- THEMES 2025Mediterranean climate response to large volcanic eruptions in large ensemble simulationsMisios al.2025
- MedGU 2025Impact of cloudiness on future variability of PV power generation in the Eastern MediterraneanPapadimitriou al.2025
Climate change introduces variability in solar-based power generation, with cloudiness being a key modulating factor. The Eastern Mediterranean has been identified as a climate hotspot, making this region particularly relevant for such as-sessments. Solar energy modelling provides a robust frame-work for extending solar resource analyses to projections of photovoltaic (PV) power generation. In this study, we per-formed simulations of PV output power with the Global Solar Energy Estimator (GSEE), with input surface solar radiation and temperature data from three global climate models that participated in the 6th phase of the Climate Model Intercom-parison Project (CMIP-6): CNRM-CM6-1-HR, INP-CM5-0, and MPI-ESM1-2-HR. Projections were evaluated under three different Shared Socioeconomic Pathways (SSPs 245, 370, 585), focusing on four major cities in the region: Athens, Al-exandria, Istanbul and Nicosia. Both all-sky and clear-sky Global Horizontal Irradiance (GHI) were used as input to GSEE, with the contribution of cloudiness further examined through a comparison with the Cloud Modification Factor (CMF), defined as the ratio of all-sky to clear-sky GHI. Moreover, we investigated the sensitivity of system configu-ration to cloud-related variability, by simulating PV plants with fixed panels, single axis, and dual-axis tracking systems. The results indicate consistent shifts in solar resource availa-bility across scenarios, reflecting alterations in cloud patterns and distribution, and highlighting the role of climate change in shaping the long-term potential of PV power generation.
- LPS 2025Solar Irradiance Variability, its Uncertainty and Impact on the Earth AtmosphereMargit Haberreiter , Stergios Misios, Nigel Fox , and 2 more authors2025
Solar irradiance varies on time-scales from minutes, days, to months, decades, centuries and beyond. To fully understand the effects of solar irradiance variations on the Earth's atmosphere high-precision measurements as well as robust irradiance reconstruction models are required to fill the gaps when no measurements are available. Here, we present latest work on the uncertainty in atmospheric heating fluxes and the responses of the thermal and chemical structure of the upper atmosphere. We present the solar irradiance input uncertainties as determined within the framework of the TRUTHS mission Accompanying Consolidation Towards Operations Study (TACOS). Our atmospheric and climate model simulations allow us to estimate uncertainties in the atmospheric state for solar spectra of different activity level. The results are compared to the modelling results using the CMIP6- and the forthcoming CMIP7-recomended solar spectra. In addition, we will also report on further related solar irradiance studies within TACOS.
- COMEACAP 2025Mediterranean amplification in the LESFMIP simulationsMisios al.2025
The Mediterranean region is particularly sensitive to climate change as it is located at the crossroads of atmospheric processes. In the Mediterranean, and particularly in its eastern parts, the rate of warming is more pronounced than the global mean rate of warming, with projected increase up to 2.5-3.0 °C and simultaneous decrease in precipitation by the end of the century. Here, we investigate the contribution of different climate drivers to regional warming trends in the historical period, focusing in the summer season. We are analyzing surface and atmospheric temperature trends in simulations from the latest Large Ensemble Single Forcing Model Intercomparison Project (LESFMIP). Specifically, we analyze simulations under the a) historical, b) hist-GHG, c) hist-aer, d) hist-volc and e) hist-sol, experiments which enable the detection of responses to individual forcings over the historical period. The large ensemble size in the simulations facilitate the detection of forced signals on regional scales in the presence of internal variability. Model results are compared with trends in reanalysis datasets and long-term radiosonde soundings in selected locations in the eastern Mediterranean. Our analysis highlights the important role of aerosols in the observed summer-time temperature trends in the Mediterranean and mechanisms are discussed. Aerosol changes particularly after 1980 combined with post-eruption trends explains most of precipitation increases in the Mediterranean. Consistent with the surface amplification, the strongest warming in the upper troposphere is found in the June-July-August (JJA) season. Mechanisms explaining temperature and precipitation trends are discussed. The analysis has been conducted under the Large Ensembles for Attribution of Dynamically-driven ExtRemes (LEADER) activity and has been financed by the Public Investment Program of the Greek Ministry of Education, Religious Affairs and Sports.
- COMEACAP 2025ClimateHub: Seasonal to decadal predictions for national renewable energy managementKartsios al.2025
ClimateHub is the first National Collaboration Programme (NCP) in Greece supported by the Copernicus Climate Change Service (C3S). ClimateHub aims at delivering innovative services to national authorities regulating the energy sector by developing climate-based tools and services building on the C3S experience. As a service provider, ClimateHub will fill the knowledge and service gap on climate information at time scales exceeding the typical weather forecast. Two time horizons have been chosen, in which previous demonstrators in the C3S energy sector have shown considerable potential, specifically a) seasonal and b) decadal. Through a co-design approach, ClimateHub has identified three applications where public authorities have virtually no access on climate-related impacts on the renewable energy sources (RES) sector at these time scales, a) energy demand, b) solar power and c) wind power. This is consistent with the national plans described in the National Energy and Climate Plan (NECP), which projects RES generation mainly from solar and wind installations by 2030. During its first phase, a novel pre-operational prediction system based on the C3S seasonal forecasts and decadal predictions has been designed and developed to address national needs in climate information for RES production. In its second phase, skillful long-term predictions of essential climate variables such as wind speed, solar radiation, and surface temperature inform the energy industry about expected renewable energy production and energy consumption, and further prepare the sector for any possible risks, which may arise due to anomalies. In a nutshell, ClimateHub provides actionable climate and energy products to the national authorities, from a) seasonal and decadal predictions on climate-related electricity demand, b) seasonal forecasts of solar PV and onshore/offshore wind energy production and decadal outlooks in PV and offshore wind energy production, specifically in the summer, through its dedicated web portal (https://portal.climatehub.gr).
- SWIMTerrestrial Atmospheric and Climatological Responses to Recent (2-3 Mya) Encounters with Dense Interstellar CloudsMiller al.2025
Recently, Opher et al. (2024) proposed that the Solar System passed through a dense interstellar cloud called the Local Lynx of Cold Clouds 2-3 million years ago. Due to the cloud’s high density and ram pressure, it would have greatly compressed the heliosphere to within Earth’s orbit, exposing Earth directly to the interstellar medium. Prior investigations into these events have used simple models and scaling relations. In this study, we utilize for the first time a state-of-the-art 3D climatological model (CESM/WACCM) to demonstrate the effects of interstellar hydrogen in Earth’s atmosphere. We examine how this source of high-altitude hydrogen modifies the chemistry and dynamics in the stratosphere and mesosphere. In particular, there is a broad depletion of mesospheric ozone and a corresponding decrease in temperature. We conclude with a discussion of potential surface effects.
- EGU 2025Summer-time Mediterranean amplification to different climate driversMisios al.2025
The Mediterranean region is particularly sensitive to climate change as it is located at the crossroads of atmospheric processes. In the Mediterranean, and particularly in it’s eastern parts, the rate of warming is more pronounced than the global mean rate of warming, with projected increase up to 2.5-3.0 °C and simultaneous decrease in precipitation of 15 % by the end of the century. Here, we investigate the contribution of different climate drivers to regional warming trends, focusing in the summer season. We are analyzing surface and atmospheric temperature trends in simulations from nine climate models participating in the Precipitation Driver and Response Model intercomparison project (PDRMIP). The model simulations have assumed idealized and abrupt forcing applied in global scale, specifically: doubling the CO2 concentrations, 10 times the present-day black carbon concentrations, 5 times the SO4 concentration, 3 times the CH4 concentration and 2% increase in total solar irradiance (TSI). Model results are compared with trends in reanalysis datasets and long-term radiosonde soundings in selected locations in the eastern Mediterranean. Increases in CO2, CH4 and TSI cause a very similar seasonal variation of the temperature amplification, with a stronger magnitude simulated at the upper troposphere. Consistent to the surface amplification, the strongest warming in the upper troposphere is found in the June-July-August (JJA) season. SO4 causes a stronger upper tropospheric temperature amplification, particularly in July and August. BC aerosols, on the other hand cause a considerably stronger amplification in the JJA season which spreads to the upper troposphere the following months. Our analysis highlights the important role of aerosols in the observed summer-time temperature trends in the Mediterranean and mechanisms are discussed.
- EGU 2025Changes in the spectral composition of surface solar radiation under the presence of stratospheric aerosols: a case study for the Pinatubo eruptionFountoulakis al.2025
The presence of aerosols in the stratosphere alters the spectral shape, the amount and the spatial distribution of the solar light that reaches the Earth surface. Such changes in surface solar radiation have been discussed in a few studies, but the role of the underlying tropospheric aerosol layer in the presence of stratospheric aerosols has not been considered. In this study we investigate the changes in the direct and global spectral surface solar irradiances following the extremely intense volcanic eruption (VEI=6) of Mount Pinatubo (15°N, 120°E) in June 1991. The eruption of Mount Pinatubo ejected massive loads of sulphate and ash particles into the stratosphere, which covered the entire globe after three weeks and then remained in the stratosphere for several months. In the aftermath, major perturbations of the stratospheric ozone layer and the near-surface temperature have been documented. Here, we provide model-derived stratospheric aerosol optical properties, constrained by ground-based and airborne remote sensing and in-situ data, to the radiative transfer model libRadtran to calculate the spectral surface solar irradiance in the wavelength range 350 – 750 nm. Radiative transfer simulations have been performed for two European sites where in situ measurements of the aerosol extinction profile were available a few months after the eruption, assuming different concentrations and types of tropospheric aerosols present in the atmosphere along with the overlying stratospheric volcanic layers, as well as different solar zenith angles. Changes in the spectral composition and the distribution of surface solar radiation in the considered spectral range play a key role in many biological processes (e.g., photosynthesis), as well as in solar energy production. Thus, our results provide insights on how such processes could be impacted after future volcanic eruptions or under solar radiation modification scenarios.