The goal of QUAERERE (Latin for researching) is a reliable, observations-based, global quantification of aerosol indirect effects, which would also imply a constraint on climate sensitivity and thus climate predictions. This goal is now reachable combining recent advances in different disciplines: (i) a decade-long satellite dataset involving retrievals of the relevant quantities is now available, complemented by a complete aerosol dataset from a new reanalysis; (ii) on the basis of high-resolved numerical weather prediction models, which include parameterisations of aerosol cycles and cloud-precipitation microphysics, cloud-system resolving simulations at a regional scale are now possible; reliable simulations beyond idealised cases are thus possible. These tools are complemented by comprehensive global climate models and reference ob servations from ground-based sites. The problem in aerosol-cloud-climate effects is in its complexity: Various processes counteract each other, and large spatiotemporal variability of clouds buffers the forcing effects. QUAERERE proposes a two-fold divide-and-conquer approach to this complex problem: (i) aerosol-cloud-climate effects will be investigated by regime; this allows to circumvent the problem of aerosol-cloud-climate effects being buffered when averaging over different regimes; and (ii) by investigating individual terms contributing to the aerosol-cloud-climate effects separately; this allows to analyse individual statistical relationship in satellite observations and model results consistently, and to perform model sensitivity studies for cause-effect attribution. QUAERERE is funded by European Research Council (Call ERC-2012-StG, PE10, FP7 ideas starting grant 306284).