The gaseous and particulate matter emissions due to volcanic activity may have important impacts on the tropospheric and stratospheric composition, the distribution and properties of low and high clouds, the regional- to global-scale radiation budget, and then climate. Volcanic emissions have been identified as one of the largest sources of uncertainty in our understanding of recent climate change trends. The main contributors to radiative forcing from volcanoes are the long-lasting sulphate aerosols (SA) formed by the gas-to-particle conversion of sulphur dioxide (SO2) emissions. Mt Etna is one of the most important natural emitters of gas and particles on Earth, accounting for about 10% of the global average volcanic emissions of carbon dioxide and a regionally relevant amount of SO2. The total mass of gaseous sulphur compounds emitted by Etna in the central Mediterranean, through its continuous passive degassing and episodic explosive eruptions, corresponds to about ten times as much the total anthropogenic sulphur emissions in the same area. The Mediterranean basin is a sensitive climate hot-spot and a crossroad of pollutants from different local to intercontinental sources. Thus, it is crucial to disentangle and better understand the different sources of radiative forcing, which can have here a larger impact on the biosphere than in other regions. The impacts of Etna’s emissions on the atmospheric composition, aerosol and clouds optical properties and regional climate in the Mediterranean, even if recently identified as possibly important, are not yet systematically studied nor quantified on relatively long timescales. The DICIT project aims at quantifying, for the first time, the decadal direct radiative forcing of Mt Etna’s sulphate aerosol and its indirect effect via aerosol-cloud-radiation interactions, thus helping to shed light on its impact in the Mediterranean climate hot-spot. This project is organised into 3 work packages (WP), exploring and linking the volcanic emissions, plumes evolution and dispersion processes and downwind impacts, at increasingly larger spatial scales: WP1: Near-source characterisation of Mt Etna’s volcanic aerosols emissions and related processes; WP2: Mt Etna’s plume dispersion and regional evolution processes (including a new observatory); WP3: Estimation of direct and indirect climatic impacts of Etna's emissions in the Mediterranean basin. The overall objectives of the DICIT project are: (a) to characterise the Mt Etna's aerosol source as a function of its volcanic activity type, (b) to quantify the role of Mt Etna on the Mediterranean sulphur budget and the downwind perturbation of the aerosol layer and clouds occurrence and properties, (c) to quantify the regional radiative forcing of continuous degassing and explosive eruptions, and (d) to develop new observations and modelling tools to study volcanic plumes. From a methodological perspective, the DICIT project is based on the synergy of information coming from surface and satellite observations, and chemical, dynamics and radiative modelling. A series of 4 field campaigns to characterise the volcanic aerosols at the crater-proximal scale, new models/observations developments, and the establishment of a new observatory in a poorly covered area (South Peloponnese, in the region of prevalent dispersion of Mount Etna's plumes) are foreseen in this project. The project gathers 4 leading French laboratories in Atmospheric/Climate Science (LISA, LMD, LOA) and Solid Earth (LG-ENS) around a common research axis and thus constitutes a structuring theme for the French community. The projet includes also international partners from 5 European countries. Mt Etna is a typical case of a continuously degassing volcano, so the methodologies developed in this project will provide a benchmark for several other passive degassing volcanoes at the global scale, with a very large potential benefit for the international scientific community.