I know the intended purpose of this sentence is that it shocks, but I'm not sure I'm in a position to evaluate "5 Hiroshima bombs" any more clearly than if it were presented as a metric (joules in this case) I seldom use. Would it be wrong to call it click-baity? "2019 - Yet Another Year of Record-Setting Ocean Warming" would be equally alarming to me, but I'd also understand what it means.