Temperature-dependent fluorescence of YAG:Ce was studied as an example of a spectral characterization method. According to the steady-state emission at various temperatures, four types of temperature sensing functions were retrieved using behaviors of 1) wavenumber at emission band maximum magnitude, 2) wavenumber of emission band barycenter, 3) emission bandwidth, and 4) the ratio of intensities at different wavelengths in the emission band. All four types of functions demonstrate a near linear relationship with temperature in the measured temperature range. Function No. 2 shows finer precision than function No. 1, while they have the same meaning in physics. Mechanisms of the temperature dependence are discussed after a brief review of emission peak shifts of Ce 3+ -doped garnets. Function No. 3 shows an abnormal narrowing of the band with increasing temperature which can be related to the narrowing ground levels' splitting gap. In the experiment, the two novel spectral characterization methods showed their advantages: the barycenter technique contains the smallest uncertainty, and the self-referenced intensity ratio technique provides flexible ratiometric sensing functions for various measurement needs. Seshadri, "Rapid microwave preparation of highly efficient Ce 3+ -substituted garnet phosphors for solid state white lighting," Chem. Mater. 24(6), 1198-1204 (2012). 10. S. P. Ying, P. T. Chou, and H. K. Fu, "Influence of the temperature dependent spectral power distribution of light-emitting Diodes on the illuminance responsivity of a photometer," Opt. Lasers Eng. 51(10), 1179-1184 (2013). Defects Solids 158(1-6), 39-47 (2003). 14. M. Grinberg, "High pressure spectroscopy of rare earth ions doped crystals -new results," Opt. Mater. 28(1-2), 26-34 (2006) 8-12 (2015).