46 pgs + 23 gifsGreenhouse gases are causing atmospheric warming. The effects upon our earth are subtle but are very important in the years to come. Water vapor and carbon dioxide are the major causes but methane, nitrous oxide and sulfur hexafluoride also factor in. Water vapor keeps some heat from leaving the earth and also increases water levels by helping to melt earth ice. Carbon dioxide mostly from burning fossil fuels also helps keep heat f