GRE Reading Comprehension
Scientists warn of a global warming, a "greenhouse effect" resulting from increased atmospheric pollutants, including carbon dioxide from the burning of wood, coal, and oil. A coal-industry spokesperson says that the effect need not cause concern in the near future if, as some scientists believe, the Earth faces another ice age within the next thousand years, since each calamity could cancel out the other.
Which of the following, if true, casts the most serious doubt on the conclusion of the spokesperson?
- A There is a generally cyclical pattern in the recurrence of ice ages on Earth.
- B The disastrous results of the greenhouse effect have begun to occur and will probably intensify within the next fifty years.
- C Trees absorb some of the carbon dioxide in the lower atmosphere and produce oxygen, which is not a pollutant.
- D Much of the carbon dioxide currently being produced comes not from coal but from the burning of trees cleared from large areas of tropical rain forest.
- E The greenhouse effect is a scientific conjecture based on incomplete data about gases in the upper atmosphere and on a theory about how those gases could affect the heat from the Sun.
Correct Answer: B