What role do aerosols play in mediating the impact of solar variability on climate ? Benjamin Laken, from the Astrophysical Institute of the Canarian Islands, discusses with us this question. This movie was produced by COST action TOSCA (Towards a more complete assessment of the impact of solar variability on climate), a multidisciplinary European network of scientists from 20 countries whose objective is to provide a better understanding of the hotly debated role of the Sun in climate change. For more information, and more movies, see http://www.tosca-cost.eu