Global warming is caused by the release of carbon dioxide and other heat-trapping gases into earth's atmosphere. The gases act like a thick blanket, trapping the sun's heat and causing the planet to warm up. Increase the gases and the warming increases, too. These gases are created when we burn fossil fuels in our cars and power plants as well as by loss of forests and agriculture.

Scientists find clues to global warming by studying remnants of the past in ancient glacial ice, ocean sediments as well as tree and coral rings. Global warming is problematic to human civilization because it will cause increasingly severe storms and droughts, glaciers to melt, rising seas, changes in weather patterns, and the spread of disease.
Automobiles and coal-burning power plants are the two biggest sources of carbon dioxide in the U.S. Clearing of forests is also an important source worldwide. Scientists say that unless we curb global warming emissions, average temperatures could rise by 3 to 9 degrees by the end of the century.

SURPRISING SCIENTIFIC STATISTICS ON GLOBAL WARMING
Recent data from Antarctic ice cores indicate that carbon dioxide concentrations are now higher than at any time during the past 650,000 years, which is as far back as measurements can now reach.

2005 was the warmest year on record since atmospheric temperatures have been measured. The ten warmest years on record have all been since 1990. In summer 2005, heat records were broken in hundreds of U.S. cities. Over the past 50 years, the average global temperature has increased at the fastest rate in recorded history.