Page 26 - Alternative Energy Systems in Building Design

NATURAL FACTORS DRIVING CLIMATE CHANGE 3

Figure 1.2 Temperature and CO 2 concentration in the atmosphere over the
past 400,000 years (from the Vostok Ice Core). Courtesy of United Nations Environmental
Program/GRID-Arendal.

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levels of 280 ppm . These measurements have been substantiated by verifying the
dynamic equilibrium of vast amounts of CO gas held in the world’s oceans, which
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move into and return from the atmosphere (Figs. 1.2 and 1.3).

SOLAR VARIATION
Variations in sunspots and solar flare activity, which significantly affect the earth’s
temperature, also have been observed and studied for several centuries. As we know,
the sun is the ultimate source of essentially all heat in the climate system. The energy
output of the sun, which is converted to heat at the earth’s surface, is the most signifi-
cant factor controlling the earth’s climate. Ever since the Big Bang, the sun, which is
a nuclear fusion reactor furnace, has been burning by converting hydrogen into helium
and is getting brighter by outputting higher amounts of energy. In its earlier days, the
earth went through several extreme cold and hot periods when liquid water at its surface
was completely frozen and liquefied several times, a phenomenon referred to as the faint
young sun paradox.
Recent climatology studies have determined that the sun undergoes 11-year cyclic
modulations. The 11-year sunspot cycle, however, has so far not been established as
having a definitive effect on the global climate. Solar intensity variations, though, did
have influence in triggering the global warming effect recorded from 1900 to 1950.