The truth can be a bitter pill to swallow and An Inconvenient Truth contains the active ingredients: evidence of disruption of the Earth's atmosphere, biosphere, bathysphere, and cryosphere (ice cover). It shows how climate change presents the greatest challenge—and the grandest opportunity—facing the human race.

Hyperbole? Not according to Al Gore, who “used to be the next President of the United States,” as he breaks the emotional ice at the start of this fast paced film. With humour, humility, intelligence, and artistry, the film shows him traversing the globe. It paints a portrait of “Earth in the Balance” (the title of his 1992 book), perilously perched on a series of potential climatic tipping points.

Earth's polar ice caps have remained medium to large in size for more than 650 000 years, switching in tandem with levels of atmospheric carbon dioxide (CO₂), ranging from 180 to 280 parts per million (ppm). At the current CO₂ level of 380 ppm we are outside that envelope …