We thought he was joking at first, but then we realized that he was 'in earnest'. [=he was being serious]
It's hard to tell if he's making this proposal 'in earnest'.
It began to rain 'in earnest' [='heavily'] in the evening.
(..) Do you... Do you often entertain suicidal thoughts? No, I'm more homicidal in nature. Pretty sure you're not saying that in earnest, but as a way to keep me at arm's length. I'm here. What's up? Oh, do you mind? I have work to do. You need to talk about (..)2008 TvShow: Bones Title: The Finger in the Nest Season: 4 Episode 3