Multi-wavelength observations are mandatory to understand the physical properties of astrophysical sources. In this paper we use observations in the far infrared to radio range to derive the spectral energy distribution (SED) of the Carina nebula. To do this, we carefully subtract the irregularly varying diffuse emission from the Galactic plane, which can be of the order of 10 of the nebula flux at these wavelengths. We find that the far infrared SED can be modeled as emission from a dust population with a single temperature T_d=(34.5^{+2.0}_{-1.8}), and with a spectral index of emissivity alpha=-1.37^{+0.09}_{-0.08}. We also find a total infrared luminosity of the Nebula of (7.4^{+2.5}_{-1.4})x10^6 L_{⊙} and, assuming a single temperature of the dust, a mass of the dust of (9500^{+4600}_{-3500})M_⊙. ; Comment: 33 pages, 4 figures. Published in ApJ. Improved study of the diffuse background emission and of the data analysis. Added a discussion concerning the discrepancy between the WMAP and the Parkes data