Other trace gases in the earth's atmosphere also absorb infrared
energy. Carbon dioxide, nitrous oxide, methane, ozone, and the CFCs are
all greenhouse gases. They absorb and re-radiate infrared radiation both
upward and downward and contribute to maintaining a surface temperature
that is higher than it would be in their absence. We have seen in our study
of atmospheric chemistry that many of these trace gases are produced by
humans through the use of combustion engines and other activities. By increasing the
atmospheric concentrations of these gases, we are contributing to an
enhanced warming of the earth's surface by the increased greenhouse effect.
We will come back to this topic as we seek to quantify the magnitude of
this effect.
NEXT: Quantifying the Global Energy Balance