Read Behavioral Objective 20 and the read in the text those pages indicated by Z-14 . The two gases in the atmosphere that are mainly responsible for absorbing the 30 percent solar energy discussed earlier are carbon dioxide and water vapor. This process is called the greenhouse effect. If it were not for the greenhouse effect the average air temperature at the Earth’s surface would be only -18 degree C. The marked increase in atmospheric carbon dioxide concentration during the last 150 years has recently caused concern among ecologists and environmentalists because of its effect on global temperature. Scientists continue to debate how increasing levels of atmospheric carbon dioxide will affect the temperature. Several models predict that a doubling of carbon dioxide concentration, which could occur by the end of the next century, might produce an average temperature increase of 4 degrees C.

What is the source of carbon dioxide in the atmosphere which has increase during the past 150 years?

a. cellular respiration by the consumers

b. burning of fossil fuels buried in the ground

c. A decrease in the amount of plants (producers) to fix the carbon dioxide into organic molecules.

What would be a worst-case scenario if the atmosphere was to absorb more solar energy due to an increase in carbon dioxide levels?

a. A melting of polar ice causing an increase in the sea level, flooding coastal areas.

b. It would allow plant growth to occur at a faster rate at the expense of consumers.

c. It would cause the relocation of the polar ice caps farther south.

d. It would stimulate the ozone layer to become smaller.