Page 191 - Fundamentals of Air Pollution 3E

I. Global Warming

Fig. 11-1. Mean monthly concentrations of atmospheric CO 2 at Mauna Loa. The yearly
oscillation is explained mainly by the annual cycle of photosynthesis and respiration of plants
in the Northern Hemisphere. Source: Lindzen (2).
primarily the oceans and polar regions; and the urban sprawl toward loca-
tions at which temperature measurements are made, such as airports.
Although there has been a warming trend over the past 100 years, it is
not necessarily due to the greenhouse effect. The concern of the scientific
community about accelerating changes in the next 40 to 50 years is based
not only on the recent observations of temperature compared with past
observations, but also on the physical principles related to the greenhouse
effect.
Global climate models have been used to estimate the effects in terms
of temperature changes. Considerable difficulties are encountered in at
least two areas. One is the difficulty in accounting properly for moisture
changes including cloud formation. An important mechanism of heat trans-
fer is through water vapor and water droplets. Of course, cloud cover alters
the radiational heating at any given time. The second difficulty is accounting
for solar radiation variability and the occasional injection of fine particulate
matter into the atmosphere by volcanic activity, both of which alter the
amount of solar radiation reaching the ground. Results from most model
attempts suggest that global average surface temperatures will increase on
the order of 1.5°C to 4.5°C over the next century.
The greatest concern about global warming is the regional and seasonal
effects that will result. Of considerable significance could be changes in
the patterns of precipitation in the agricultural and forested regions during
the growing seasons in particular.
The Intergovernmental Panel on Climate Change (IPCC) was established
in 1988 by the World Meteorological Organization (WMO) and United
Nations Environment Program (UNEP). This panel gave its official report