If he isn't deliberately omitting information that would lead to a different conclusion -- deceit -- or using emotional manipulation to imply facts not in evidence -- also deceit -- then he's simply wrong.
In the case we're talking about, the emotional impact intended is simply that the information is alarming. You can drily say "the house is on fire", or with flushed face and wide eyes exclaim "the house is on fire!" The latter involves emotional information in addition to the relevant facts. If the house is not on fire, both statements have the same problem: they are false. If the house is on fire, the second is more likely to prompt action. The absence of emotional cues in the first statement will itself be taken as an emotional cue by an ordinary audience. "The house can't be on fire in the way I would normally interpret 'the house is on fire' because that would cause panic, and the speaker isn't panicking. Ho, hum. Are there any sports on?" In fact, the dryness of the presentation is frequently presented as evidence that climate change is a fraud. Denialists say "if you really believed this is true, you'd be doing X, and you aren't, so ha!" The beauty of this gambit is that the goal posts are so mobile. If you do X, they pull secret expected behavior Y out of their pocket and repeat the argument. These measures of sincere affect are like sharks teeth. There is always another if you pull out the one you see. You're damned if you do and you're damned if you don't. So, setting aside these particular denialists as insincere, one's best bet is to try to indicate your affect in your presentation, because this is a heuristic ordinary people use to gauge the honesty of their interlocutors: does the implied urgency of their argument match their tone.