For an emissivity of 1.0000 this gives temperatures of 289.08 or 289.15 K respectively i.e. 15.93 or 16.00 C. It is generally believed that the actual mean global surface temperature is closer to about 15 C i.e. ~288.15 K. Thus the mean emissivity would be closer to 0.996, not the 0.96 quoted by Monckton.