The White House Press corps does fly commercial, UAL typically gets the charters, only a small number of the press corps fly on AF1. Also, don't forget about pre-positioning the motorcade vehicles - it used to be a C141, may be a C17 now.

So aside from the carbon emitted from AF1, there is also the carbon from the press charter and the motorcade cargo aircraft. I wish the press would get it's facts straight.