The film includes many segments intended to refute critics who say that global warming is insignificant or unproven. For example, Gore discusses the risk of the collapse of a major ice sheet in Greenland or West Antarctica, either of which could raise global sea levels by approximately 20 feet (6m), flooding coastal areas and producing 100 million refugees. Meltwater from Greenland, because of its lower salinity, could halt the Gulf Stream current and quickly trigger dramatic local cooling in Northern Europe.
In an effort to explain the global warming phenomenon, the film examines annual temperature and CO2 levels for the past 600,000 years in Antarctic ice core samples. An analogy to Hurricane Katrina is used for those familiar with the 30-ft to 45-ft (9 to 14m) waves that destroyed almost a million homes in coastal Mississippi, Louisiana, Alabama, and Florida.
The documentary ends with Gore noting that if appropriate action is taken soon, the effects of global warming can be successfully reversed by releasing less carbon dioxide and growing more plants or trees. Gore calls upon viewers to learn how they can help in this initiative.
Gore's book of the same title was published concurrently with the theatrical release of the documentary. The book contains additional, detailed information, scientific analysis, and Gore's commentary on the issues presented in the documentary.
Scientific basis
Main article: Scientific opinion on climate