New trends in physics teaching, v.4; The ... - unesdoc - Unesco

A solar unit
polar ice caps would melt and shorelines everywhere would be inundated. (Actually, however,
the power consumption in major metropolitan areas is in some cases of the order of 0.1 solar
unit over those areas - and their mean temperatures are raised by several degrees in consequence.
New Yorkers keep their whole city warm!)
Moving down the scale, we now come to situations that are less hypothetical. If world-wide
power generation were equivalent to 1/100 of a solar unit, the world mean temperature would
rise by about 1 K. As Rose says, ‘At this point, experts may disagree on whether such a temperature
rise would have major effects on the ice caps, the cloud cover, the weather patterns and the
distribution of plant and animal life. Whatever the arguments may be, pro or con, it is not the
sort of experiment the world should choose to explore.’ Yet such a temperature rise appears to
be the likely consequence, through the greenhouse effect, of continuing to increase the carbon
dioxide content of the atmosphere by the burning of fossil fuels at their present rate for another
century or so.
Going down another factor of 10, we have l/lOOO of one solar unit. This corresponds to the
present level of power generation in the United States. That is, the total power now generated
in the United States is equal in amount to 0.1 per cent of the total solar radiation falling on the
country.
For the world as a whole, the total power generated is at present only 1/10 000 of a solar
unit - i.e. the equivalent of 0.01 per cent of all the solar power received by the earth. However,
there are at least two factors operating to increase this figure. First, the population of the world
is continuing to increase at a rapid rate, and seems destined to double, or more, within much
less than a century. Second, the urge toward a higher standard of living wil certainly cause the
energy usage per person in the developing countries to rise and perhaps to approach the United
States level. It is thus not at all unlikely that global energy production and use wil come to
exceed 1/1000 of a solar unit, and will be enough to create concern about climatic changes of
the sort mentioned above.
The magnitude of this projected global demand for energy suggests that, rather than accepting
it as a need that must somehow be supplied, we ought to look very critically at the way
energy is squandered in a high-technology society. Albert Rose, after presenting the above
estimates, points out that the ‘good life’ in the United States involves an average power usage
of about 10 kilowatts per person, whereas only about 100 watts is needed to keep the human
machine going (equivalent to one medium power light bulb). Thus North American society
uses the energy equivalent of 100 servants for eaeh citizen - a hundred times the energy we
need to stay alive. In Rose’s words, ‘flipping on a 100 W bulb is the energy equivalent of adding
another servant. Stepping on the accelerator of an automobile in anticipation of a green light
calls forth the equivalent of over 1000 servants pushing on the rear end of the car and would
have been the envy of any Pharaoh.’ It is obvious that any significant retreat from this lavish
existence would be strongly resisted by any society that now enjoys it. Indeed, the present
predictions are that the demand for electrical power in the United States will double in the
next decade or so. But, if humanity as a whole is to aspire to a comfortable standard of living,
we had better watch those solar units - and the ‘haves’ must be prepared to make some concessions.
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