Comparing Irradiance Reconstructions from HMI/SDO Magnetograms with SORCE Observations K. L. Yeo1, S. K. Solanki1,2, N. A. Krivova1 1 2 Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany; School of Space Research, Kyung Hee University, Yongjin, Gyeonggi, Korea There is growing evidence the variation in solar irradiance, measured since 1978, has an effect on Earth's climate. Of the models proposed to account for the observed variance, the most successful are based on the assumption that the evolution of the solar surface magnetic field is directly responsible. The reliable modelling of irradiance variation under this assumption is contingent on the availability of high-quality full-disc magnetograms. Before HMI/SDO was operational, MDI/SOHO observations were the best available and employed extensively for the purpose. The use of HMI observations, which surpasses the MDI both in terms of resolution and noise performance, represents the next step forward in progressing said models. Also, after MDI is taken offline, HMI will be the only space-borne sensor returning full-disk magnetograms. Here we present preliminary total and spectral irradiance reconstructions from HMI observations and compare them to corresponding TIM and SIM measurements from the SORCE mission.