What's true for scare-tactic HIV PSAs also holds for climate change commercials:
Matthew Feinberg at the University of California, Berkeley, wondered whether presenting children as the main victims of climate change, a common feature of warning messages, might be viewed as unfair because children have not caused global warming. He speculated that this, along with the apocalyptic descriptions of global warming's possible consequences, might threaten people's natural tendency to believe that the world is a fundamentally fair and stable place. Undermining that belief has been shown to increase the likelihood that people will ignore reality and allow events to unfold around them without intervening.
Cord Jefferson rounded up some of the more depressing ads.