The dependence of an emission wavelength on the crystal temperature was first investigated for a diode-pumped continuous-wave ${{\rm Yb}^{3 + }}$Yb3+-doped ${{\rm CaGdAlO}_4}$CaGdAlO4 (Yb:CALGO) laser. A maximum output power of 11 W was obtained, corresponding to a slope efficiency of 19.8%. The output wavelength varied from 1051.10 nm to 1054.72 nm with increased absorbed pump power. This wavelength shift is attributed to a change in the crystal temperature. This observation is, to our best knowledge, an original conclusion about this phenomenon in a Yb:CALGO laser. We use a temperature-dependent model to explain the emission wavelength shifts that can be generalized to any such quasi-three-level materials.