The CMCC Foundation (Fondazione Centro Euro-Mediterraneo sui Cambiamenti Climatici) routinely operates a Global Seasonal Ensemble Prediction System (CMCC-SPS) based on a Coupled Atmosphere-Ocean-Land-Cryosphere Global Model. Every month, on the 1st of the month, a set of initial conditions representing the current state of the Earth's Climate System is prepared to initialize fifty numerical simulations which, together, provide an ensemble forecast for the following six months. Forecasts' calibration and verification scores are based on a complete set of hindcasts (re-forecasts) constituted by 40-member monthly ensemble seasonal forecasts spanning the period 1993-2016.