Al Gore shows that the levels of atmosphere carbon dioxide have varied throughout Earth's history. In the graph, the carbon dioxide levels have significantly increased recently. It is the highest the level has ever been and is expected to continue to rise. In his presentation, he shows that the levels of carbon dioxide in the atmosphere have a direct correlation to the temperature of the Earth. If carbon dioxide levels go up, so does the Earth's temperature. He states that this is important because the temperature of the Earth affects the weather as well as the disappearance of the polar ice caps. He makes this point about carbon dioxide levels to encourage the people of the world to do something before global warming becomes an even larger problem.
The reason lies in the structure of the eye itself. Nocturnal animals tend to have proportionally bigger eyes than humans do. They also tend to have pupils that open more widely in low light. So, at the outset, nocturnal eyes gather more light than human eyes do.
