“Frozen Planet,” the seven-hour series that has attracted millions of viewers to the Discovery Channel in recent weeks, shows Earth in extremis. On this planet, the poles are violently cold, yet are also atypically vulnerable to the warming trends that are endangering polar bear populations and causing huge chunks of ice to break off Greenland and Antarctica.

All of it — the struggling polar bears, the collapsing ice shelves — is shown in stunning high definition. It is accompanied by the voice of Alec Baldwin, who narrates the series and says categorically, “The ends of the earth are changing.”

What the series never assesses, however, is why.

The vast majority of scientists agree that human activities are influencing changes to the climate — especially at the poles — and believe that the situation requires serious attention. That scientific consensus is absent from “Frozen Planet,” for reasons that shed light on the dilemma of commercial television, where the pursuit of ratings can sometimes clash with the quest for environmental and scientific education, particularly in issues, like global warming, that involve vociferous debate.

Including the scientific theories “would have undermined the strength of an objective documentary, and would then have become utilized by people with political agendas,” Vanessa Berlowitz, the series producer, said in an interview.