Page 10 - Managing Global Warming

4 Managing Global Warming

H€ ogbom, had estimated that CO 2 from volcanic eruptions, together with the ocean
uptake of CO 2 , could explain how the CO 2 concentrations in the atmosphere could
change and hence provide some explanation for the ice ages. Along the way, H€ ogbom
stumbled on a strange and new idea that the CO 2 emitted from industrial coal burning
factories might influence the atmospheric CO 2 concentration. He did indeed find that
human activities were contributing CO 2 to the atmosphere at a rate comparable to the
natural geochemical processes. The increase was small compared to what was already
in the atmosphere, but if continued, it would influence the climate. Arrhenius took up
this concept, and his calculations are published in reference [6]. Arrhenius concluded
that the emissions from human industry might someday bring on global warming. As a
result, Arrhenius’s name is forever linked to the greenhouse theory of global warming.
However, thanks must also go to those who paved the way—Fourier, Melloni,
Tyndall, H€ ogbom, and probably many others.
Arrhenius’s calculations were at first dismissed as unimportant or at worst faulty.
A similar fate was met by G.S. Callendar who, in 1938, made the point that CO 2 levels
were indeed climbing [7]. It was only in the 1960s, after C D Keeling measured
the CO 2 concentration in the atmosphere and showed that it was rising rapidly, that
scientists woke up to the fact that global warming was real and that anthropogenic
activity was to blame.
Water vapor is an even more effective greenhouse gas than CO 2 . Furthermore, its
concentration in the atmosphere is very much higher than that of CO 2 (of the order of a
hundred times higher) and probably contributes about 60% of the global warming
effect. The amount of water vapor in the atmosphere is controlled by the temperature.
An increase in the CO 2 concentration in the atmosphere will increase the global
temperature only slightly, but that change is enough to increase the amount of water
vapor in the air, through evaporation from the oceans. It is this feedback mechanism
that has the greatest influence on global temperature. In a sense, paradoxically, the
concentration of CO 2 acts as a regulator for the amount of water vapor in the atmo-
sphere and is thus the determining factor in the equilibrium temperature of the earth.
Without CO 2 in the atmosphere, the temperature of the earth would be very much
cooler than it is today.
The amount of solar energy shining on the earth (with wavelengths ranging from
0.3is 5μm) is vast. It heats our atmosphere and everything on the Earth and provides
the energy for our climate and ecosystem. At night, much of this heat energy is radi-
ated back into space but at different wavelengths, which are in the infrared range from
4to50 μm [8]. This energy heats the greenhouse gas molecules (such as H 2 O, CO 2 ,
CH 4 , etc.) in the atmosphere. The explanation is as follows: using CO 2 and H 2 Oas
examples, this heating process takes place because the radiated IR frequency is in sync
(resonates) with the natural frequency of the carbon-oxygen bond of CO 2 (4.26μm
being the asymmetric stretching vibration mode and 14.99μm being the bending
vibration mode) and the oxygen-hydrogen bond of H 2 O. The increased vibration of
the bonds effectively heats the CO 2 and H 2 O molecules. These heated molecules then
pass the heat to the other molecules in the atmosphere (N 2 ,O 2 ), and this keeps
the earth at an equitable temperature. The vibrating frequencies of the OdO bond
in oxygen and the NdN bond in nitrogen molecules are very different from the
radiation frequencies and so are relatively unaffected.