Our environment is the most important resource that we have and one that we have often taken for granted. One of the environmental concerns facing the world today is the possibility of global warming resulting from a build-up of what are called greenhouse gases, some of which occur naturally. As the sun heats the earth’s surface, the earth radiates energy back into space. Atmospheric greenhouse gases trap some of this outgoing energy and retain heat. The natural greenhouse effect keeps temperatures on the earth mild enough to sustain life. However, according to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, and this warming has accelerated during the past twenty years. There is strong evidence that most of the warming over the last 50 years is caused by the build up of greenhouse gases – mostly carbon dioxide, methane, and nitrous oxide. Why is this happening? Most scientists believe that the increased use of fossil fuels to run cars and trucks, heat/cool homes, operate industry businesses, and power factories is the primary reason.
In June 2005, the U.S. National Academy of Sciences joined similar groups from nations around the world in recognition of the potential dangers ahead. They issued a call for action to reduce greenhouse gas emissions.