At the present time, 98% of the world energy consumption comes from st

At the present time, 98% of the world energy consumption comes from stored sources, such as fossil fuels or nuclear fuel. Only hydroelectric and wood energy represent completely renewable sources on ordinary time scales. Discovery of large additional fossil fuel reserves, solution of the nuclear safety and waste disposal problems, or the development of controlled thermonuclear fusion will provide only a short-term solution to the world’s energy crisis. Within about 100 years, the thermal pollution resulting from our increased energy consumption will make solar energy a necessity at any cost.

Man’s energy consumption is currently about one part in ten thousand that of the energy we receive from the sun. However, it is growing at a 5% rate, of which about 2% represents a population growth and 3% a per capita energy increase. If this growth continues, within 100 years our energy consumption will be about 1 percent of the absorbed solar energy, enough to increase the average temperature of the earth by about one degree centigrade if stored energy continues to be our predominant source. This will be the point at which there will be significant effects in our climate, including the melting of the polar ice caps, a phenomenon that will raise the level of the oceans and flood parts of our major cities. There is positive feedback associated with this process, since the polar ice cap contributes to the partial reflectivity of the energy arriving from the sun: As the ice caps begin to melt, the reflectivity will decrease, thus heating the earth still further.

It is often stated that the growth rate will decline or that energy conservation measures will preclude any long-range problem. Instead, this only postpones the problem by a few years. Conservation by a factor of 2, together with a maintenance of the 5% growth rate, delays the problem by only 14 years. Reduction of the growth rate to 4% postpones the problem by only 25 years; in addition, the inequities in standards of living throughout the world will provide pressure toward an increase in growth rate, particularly if cheap energy is available. The problem of a changing climate will not be evident until perhaps 10 years before it becomes critical due to the nature of an exponential growth rate together with the normal annual weather variations. This may be too short a period to circumvent the problem by converting to other energy sources, so advance planning is a necessity.

The only practical means of avoiding the problem of thermal pollution appears to be the use of solar energy. (Schemes to “air-condition” the earth do not appear to be feasible before the twenty-second century.) Using the solar energy before it is dissipated to heat does not increase the earth’s energy balance. The cost of solar energy is extremely favorable now, particularly when compared to the cost of relocating many of our major cities.

1. The author is primarily concerned with

(A) describing a phenomenon and explaining its causes
(B) outlining a position and supporting it with statistics
(C) isolating an ambiguity and clarifying it by definition
(D) presenting a problem and advocating a solution for it
(E) citing a counterargument and refuting it


2. According to the passage, all of the following are factors which will tend to increase thermal pollution EXCEPT

(A) the earth’s increasing population
(B) melting of the polar ice caps
(C) increase in per capita energy consumption
(D) pressure to redress standard of living inequities by increasing energy consumption
(E) expected anomalies in weather patterns


3. The positive feedback mentioned in means that the melting of the polar ice caps will

(A) reduce per capita energy consumption
(B) accelerate the transition to solar energy
(C) intensify the effects of thermal pollution
(D) necessitate a shift to alternative energy sources
(E) result in the inundations of major cities


4. The author mentions the possibility of energy conservation in order to

(A) preempt and refute a possible objection to his position
(B) support directly the central thesis of the passage
(C) minimize the significance of a contradiction in the passage
(D) prove that such measures are ineffective and counterproductive
(E) supply the reader with additional background information


5. It can be inferred that the “airconditioning” of the earth refers to proposals to

(A) distribute frigid air from the polar ice caps to coastal cities as the temperature increases due to thermal pollution
(B) dissipate the surplus of the release of stored solar energy over absorbed solar energy into space
(C) conserve completely renewable energy sources by requiring that industry replace these resources
(D) avoid further thermal pollution by converting to solar energy as opposed to conventional and nuclear sources
(E) utilize hydroelectric and wood energy to replace nonconventional energy sources such as nuclear energy


6. The tone of the passage is best describe as one of

(A) unmitigated outrage
(B) cautious optimism
(C) reckless abandon
(D) smug self-assurance
(E) pronounced alarm


7. Which of the following would be the most logical topic for the author to address in a succeeding paragraph?

(A) The problems of nuclear safety and waste disposal
(B) A history of the development of solar energy
(C) The availability and cost of solar energy technology
(D) The practical effects of flooding of coastal cities
(E) The feasibility of geothermal energy