Page 190 - Fundamentals of Air Pollution

11

Long-Term Effects on

the Planet

I. GLOBAL WARMING

Warming on the global scale is expected to occur as a result of the increase
of carbon dioxide, CO 2/ and other greenhouse gases (those that absorb
and reradiate portions of the infrared radiation from the earth). What is
debatable is the amount of warming that will occur by a particular point
in time. The CO 2 concentration has increased by about 25% since 1850 (1).
This is due to both combustion of fossil fuels and deforestation, which
decreases the surface area available for photosynthesis and the resulting
breakdown of CO 2 to oxygen and water vapor. Measurements of CO 2 for
a period of more than 25 years at the Mauna Loa observatory in Hawaii
show the rather dramatic increase (2) (Fig. 11-1). Other greenhouse gases
such as methane and chlorofluorocarbons have increased by much higher
factors.
Firm evidence for the amount of warming taking place in terms of actual
temperature measurements has been complicated primarily by the magni-
tudes of natural climatic variations that occur. A summary of the available
measurements shown by Kellogg (3) is given in Fig. 11-2. Other factors
contributing to observing trends are the length of temperature records;
the lack of representative measurements over large portions of the earth,

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