Academic publications were using the phrase "climate change" to discuss the warming effects well before Frank Luntz. He may have been important to putting that phrase in front of the general public, but "climate change" isn't a euphemism invented by PR hacks. The foremost summary assessments are assembled by the IPCC -- Intergovernmental Panel on Climate Change, whose first report came out in 1990.
Here are publications from 1980 and 1970 also using the phrase to discuss warming phenomena.
"On the Distribution of Climate Change Resulting From an Increase in CO2 Content of the Atmosphere", Journal of the Atmospheric Sciences, January 1980
https://journals.ametsoc.org/doi/pdf/10.1175/1520-0469%28198...
"Carbon Dioxide and its Role in Climate Change", Proceedings of the National Academy of Sciences, October 1970
The other irony is that this phrase was used a lot of few years back when many were claiming there was no warming going on by cherry picking the 1998 El Nino spike as a starting point for temperature graphs. Then the argument was - there is no warming, so the alarmists have stopped using the term "global warming". Of course with recent warming this particular cherry picked argument has fallen apart, but for some reason the meme persists.
I don't think the people who use the phrase even think about what they are saying. It is just part of the Gish Gallop that gets thrown out where number of words makes up for lack of solid argument (initial post that used this phrase up above being a perfect example of this)