The equivalent width of the high excitation photospheric line of C 5380A has been measured 3 to 4 times monthly in the solar irradiance spectrum since 1978. C 5380 behaves differently than other spectral lines in that it is unmodulated by the activity cycle, yet has increased in strength by 0.081 plus or minus .008 mA in 12 years. Nominal equivalent width is 22.25 mA. Implied is a temperature increase of 4.6 K which is an order of magnitude greater than constraints allowed by Active Cavity Radiometer Irradiance Monitor (ACRIM) results