Foreword
According to the National Academy of Sciences, the Earth’s surface temperature has risen by about one degree Fahrenheit over the past century, and warming has accelerated during the past two decades. Energy from the sun heats the Earth’s surface; in turn the Earth radiates energy back into space. Atmospheric greenhouse gases trap some of the outgoing energy, retaining heat to produce what is called a "greenhouse effect." Problems occur when the concentration of greenhouse gases increases, enhancing the heat-trapping capability of the Earth’s atmosphere. Some greenhouse gases — including water vapor, carbon dioxide, methane, nitrous oxide, and ozone — occur…
