I don't think that it's wrong to put the word "scientists" in quotes. Consider this: it seems that one of the 16 concerned individuals is Burt Rutan. He is a well-known aerospace engineer who has a high level of skill in a difficult technical field, and he has accomplished a great deal in his life. But is he a scientist? That might be the reason for the scare quotes.
My problem is that it justifies one of the points made in the letter, that: if you are a scientist who makes a case against global warming you are actively excluded from the scientific community.
