It has been 10 years since An Inconvenient Truth - the story of former United States Vice- President Al Gore's efforts to educate people about climate change - won the Oscar for Best Documentary Feature.

In other words, it's been far too long since we've seen a significant film on climate change. But we're going to have to keep waiting because Leonardo DiCaprio's much-hyped new National Geographic documentary Before The Flood is a let-down.

No doubt the Oscar-winner had good intentions in producing and starring in the film, which follows him as he travels the world to observe the effects of global warming, and meets scientists, statesmen and members of communities affected.

But the movie merely restates the problem in ways we have seen countless times and suffers from a lack of focus to boot.

Even if the overall message bears repeating, this feels like a wasted opportunity, especially given the platform afforded by DiCaprio's A-list status.

That status is the only consistent narrative throughline, which makes this come off as a vanity project as much as one driven by passion.

Fatally, the film cannot make up its mind who its target audience is.

If it is climate-change sceptics, there is no systematic attempt to debunk most of their common arguments, apart from the one about how global warming cannot be real because it's still freezing in the winter.

If it is people who already accept the science, the movie is preaching to the choir, and offers little by way of new analyses or prescriptions for change.

The only audience the documentary seems to make sense for are DiCaprio fans. Only then can you justify the self-indulgent opening and closing sequences about his parents' dubious choice of art for his nursery - a Hieronymus Bosch print above his crib - which he uses to make a tenuous point about the perils of a ravaged earth.

The movie does score some hits. Even if you knew the fossil fuel industry bankrolls lawmakers, it is eye-opening to see the astronomical sums funnelled to Paul Ryan and other Republican congressmen highlighted.

There is one semi-newsworthy moment, too, when Tesla founder Elon Musk states his belief that it would take only 100 "gigafactories" (like the giant one Tesla is building to make lithium-ion batteries for its cars) to switch the entire planet over to sustainable energy.

The show could have used at least five more minutes explaining the practicalities of this, but instead, viewers are whisked back to DiCaprio jetting across the globe as he surveys Alberta's oil sands and Sumatra's burning forests, stopping to gaze at cute endangered polar bears and shake hands with orangutans.

It is disappointing how little personality he brings to the table, unless you count stray observations about oil fields looking "like Mordor from Lord Of The Rings".

The only glimmer of one comes in an exchange with an Indian activist, who says she is sick of being lectured by US non- governmental organisations about how India needs to switch to sustainable energy when America cannot do that itself.

DiCaprio agrees that US energy consumption has to be the centre of climate-change talks, but he argues that it is unlikely that Americans will change their lifestyle.

It is the closest he comes to expressing a stance that isn't boilerplate activist-speak - but it also undermines his exhortation for viewers to change the way they live.

There is no shortage of distinct voices on HBO's new comedy Insecure.

Adapted from Issa Rae's award-winning Web series The Misadventures Of Awkward Black Girl, it is a sharp, funny look at the unique anxieties of being an ordinary black woman in America.

But you don't have to belong to that demographic to appreciate the show's well-observed take on race, gender and office politics.

Rae, who co-created the series with comedian Larry Wilmore, plays the charmingly awkward protagonist, Issa, who has her hands full dealing with the quotidian frustrations of an unfulfilling relationship and career. Like her best pal Molly, she is the only black person in her workplace, where white colleagues expect them to act as the resident "translators" of black culture, but then ostracise them for acting "too black".

Issa has a talent for rapping - which she mostly does to the bathroom mirror, to help her process her day - but instead spends her days working for a non-profit organisation helping at-risk kids, who constantly vex her (one demands to know why she talks "like a white girl").

Neither she nor Molly is happy with their love lives. Issa's relationship with her boyfriend Lawrence has stagnated along with his career and now she cannot stop thinking about her old friend Daniel, the one who got away.

In the six episodes previewed, the show does better as commentary than as a relationship comedy, where it isn't quite as original.

But there is enough in both columns to keep watching.