The Carbon Quandary: Essential and Detrimental - Sustainable Design: The Science of Sustainability and Green Engineering - page 274

Figure 7.6 Relative contribution
of well-mixed greenhouse gases
to the + 2.43 W m − 2 radiative
forcing shown in Figure 7.6.
Data from: Intergovernmental Panel on
Climate Change. Climate Change 2001:
The Scientific Basis , Chapter 6, IPCC,
Geneva, Switzerland, 2001.

Halocarbons,
0.34

Nitrous oxide,
0.15

Carbon
dioxide, 1.46

Methane, 0.48

in net vertical irradiance within the atmosphere, is often calculated after allowing
stratospheric temperatures to readjust to radiative equilibrium while holding all
tropospheric properties fixed at their unperturbed values. Commonly, radiative
forcing is considered to be the extent to which injecting a unit of a greenhouse
gas into the atmosphere changes global average temperature, but other factors
can affect forcing, as shown in Figures 7.5 and 7.6. Note that these radiant gases
include another family of carbon-based compounds, the halocarbons. The most
notable halocarbons are the chlorofluorocarbons (CFCs), which are notorious for
their destruction of the stratospheric ozone, but which are also greenhouse gases.

Sidebar: Applying the Synthovation/Regenerative
Model: Ozone
Ozone is an example of the need to consider the combination of relevant
factors: in this case, understanding the physics and chemistry of a situation.
The term smog is a shorthand combination of “smoke-fog.” However, it is
really a code word for photochemical oxidant smog, the brown haze that can
be seen when flying into Los Angeles and other metropolitan areas around the
world. The fact is that to make smog, at least three ingredients are needed: light,
hydrocarbons, and free radical sources such the oxides of nitrogen. Therefore,
smog is found most often in the warmer months of the year, not because
of temperature but because these are the months with greater amounts of
sunlight. More sunlight is available for two reasons, both attributed to Earth's
tilt on its axis. In the summer, Earth is tilted toward the sun, so the angle of
inclination of sunlight is greater than when the sun is tipped away from Earth,
leading to more intensity of light per Earth surface area. Also, daylight is longer
in the summer.
Hydrocarbons come from many sources, but the fact that internal com-
bustion engines burn gasoline, diesel fuel, and other mixtures of hydrocarbon