The incoming solar energy lies chiefly in the visible wavelengths from violet (400 nanometers) to red (700 nm), and the invisible wavelengths just longer than the red (the near infrared to about 1100 nm), corresponding to the surface temperature of the sun (about 5000 °Kelvin). The calculated surface temperature of the Earth for an equivalent amount of energy to escape from the Earth is 255 degrees °K (-18°C), with the single assumption that all of the terrestrial emission in the far infrared escapes directly to space. However, this assumption cannot be correct, as we know, because the average surface temperature of the Earth is about 287 °K, or +14°C. This difference of 32 ° (K or C) is the natural greenhouse effect. Most of the gases which make up the atmosphere are either diatomic or monatomic, and are transparent in the far infrared. Consequently, the only gases which absorb the terrestrial far infrared radiation are trace gases, with three or more atoms per molecule: carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), water vapor (H2O), etc., which are collectively called the greenhouse gases. Measurements in the atmosphere have established that each of the first three gases, and some others, have been increasing in global concentration over the past half-century largely because of the activities of mankind. The present concern is how much additional warming above the 32 degrees from the natural greenhouse gases will be caused by these additions to the atmosphere. Studies of ancient gases stored in ice cores taken from glaciers have shown that methane varied in its atmospheric concentrations from 0.3 to 0.7 ppm over the last 450,000 years, until the rise to the present levels began around the year 1800. Modeling of the atmosphere and some of the possible consequences of climate change, such as rising sea levels and melting of the north polar ice, will also be discussed.