Er:ZBLALiP microsphere laser has been studied under pumping by a fiber taper at 1480 nm. Whispering Gallery Mode laser spectra were analyzed for different sphere diameters and Erbium concentrations (from 0.01 % to 0.2% by mole). The gain spectrum is calculated for the transition 4I13/2->4I15/2 around 1550 nm. Red-shift effect on the frequencies of both fluorescence and laser spectra is experimentally observed when the pump power is increased, originating from thermal effects. Temperature inside the microsphere cavity and thermal expansion coefficient were determined by employing the intensity ratio of two green up- conversion emission centered at 526 and 550 nm respectively which quantitatively explain this red-shift.