Page 37 - Alternative Energy Systems in Building Design

14 GLOBAL WARMING: CLIMATIC AND ATMOSPHERIC CHANGES

livestock produces 65 percent of human-induced nitrous oxide, which has 296 times
the global-warming potential of CO , and 37 percent of human-induced methane,
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which has 23 times the global-warming potential of CO .
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ARGUMENT ABOUT THE GLOBAL CLIMATIC
TEMPERATURE BALANCE
As discussed earlier, the glacial and interglacial cycles of the last ice age provide
important information. It is believed that orbital variations of the earth around the sun
result in the growth and retreat of ice sheets. However, the ice sheets reflect sunlight
back into space and therefore cool the climate, a phenomenon referred to as the ice-
albedo feedback. Moreover, an increase in polar ice plates results in falling sea levels.
It should be noted that the expansion of ice caps also indirectly diminishes the growth
of plant life and therefore leads to reductions in CO and methane. This causes further
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cooling of the atmosphere.
Using a similar argument, rising temperatures caused by anthropogenic emissions of
greenhouse gases could lead to retreating snow lines, revealing darker ground under-
neath. Consequently, the result would be increased absorption of sunlight and thus
excess water vapor, methane, and CO generation. This eventually would act as signifi-
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cant positive feedback because increases in these levels would create an accelerated
warming trend. Water vapor, unlike other major greenhouse gases, can act as a driving
force, resulting in changing circulation patterns in the ocean or atmosphere. For instance,
a significant melting of glacial ice from Greenland would interfere with sinking waters
in the North Atlantic and inhibit the thermohaline circulation discussed earlier. This
could significantly affect the distribution of heat to in the Atlantic Ocean (Fig. 1.9).

Figure 1.9 Sea level rise owing to global warming. Courtesy of United Nations Environmental
Program/GRID-Arendal.