Climate change is one of the most significant challenges currently faced by humankind. The study of the response of the aerosol levels in the atmosphere to a changing climate and how this affects the radiative budget of the Earth (direct, semi-direct and indirect effects) is an essential topic to build confidence on climate science, since these feedbacks involve the largest uncertainties nowadays.

Air quality-climate interactions (AQCI) are, therefore, a key, but uncertain contributor to the anthropogenic forcing that remains poorly understood.

Objective: To build confidence in the AQCI studies, regional-scale integrated meteorology-atmospheric chemistry models (i.e., models with on-line chemistry) that include detailed treatment of aerosol life cycle and aerosol impacts on radiation (direct effects) and clouds (indirect effects) are in demand.

In this context, the main objective of the the visit at EMPA is the study and definition of the uncertainties in the climate-chemistry-aerosol-cloud-radiation system associated to the direct radiative forcing and the indirect effect caused by aerosols over Europe, using an ensemble of fully-coupled climate and chemistry model simulations. In this sense, the justification of the research visit has a bearing on the improvement of life quality, health and protection of ecosystems through a more precise scientific knowledge of the physico-chemical processes occurring in the climate system, as stated by the EU programme Horizon 2020.

AQMEII-Phase 3/HTAP Initiative: The visit will be developed under the umbrella of the AQMEII-Phase 3/HTAP international initiative, led by the Joint Research Center of the UE and the United States Environmental Agency (USEPA) and will contribute to the general objectives of the AQMEII collaboration framework: (1) to exchange expert knowledge in regional air quality-climate modeling; (2) to identify gaps in the knowledge of air quality-climate science; (3) to develop methodologies to evaluate uncertainty in aerosol-climate interactions; (4) to establish methodologies for model evaluation to enhance the knowledge on climate processes and; (5) to support the use of models for inter-comparison exercises.

Research Visit Objectives:

1. To validate the ensemble of simulations developed for Europe avalable from worldwide research institutions contributing to AQMEII-Phase 3/HTAP initiative.
2. To assess the direct radiative effect exerted by aerosols over Europe from the aforementioned ensemble of simulations;
3. To evaluate the aerosol indirect effect by studying the system aerosol-cloud-precipitation over the target domain.

These results will help providing improved science-based foundations to better assess the impacts of climate variability, support the development of effective climate change policies and optimize private decision-making. The expected impacts of the research visit on the origin and host institutions will cover the building of more robust, credible and trustworthy climate predictions.