Many climatologists believe that increasing atmospheric concentrations of carbon dioxide and other “greenhouse gasses“ released by human activities, such as burning fossil fuels and deforestation, are warming the Earth. The mechanism commonly known as the “greenhouse effect“ is what makes the Earth habitable. These gasses in the atmosphere act like the glass of a greenhouse, letting sunlight in and preventing heat from escaping.
Climatic modeling studies generally estimate that global temperatures will rise a few degrees Celsius in the next century. Such a warming is likely to raise sea levels by expanding ocean water and melting glaciers and the polar ice cap. A 2007 E.P.A. report confirmed that the global mean sea level rose up to three milometers per year due to global warming. In 1995, the American Medical Association warned that changes in global temperatures could introduce new infectious diseases.
No one knows for certain what the consequences of this predicted climate change will be on the quality of human life, ecosystems, and loss of arable land. Some scientists disagree with the conclusions drawn from global climate models because the effects of clouds have not been factored into the current models.