As of the late 1980’s, neither theorists nor large-scale computer climate models could accurately predict whether cloud systems would help or hurt a warming globe. Some studies suggested that a four percent increase in stratocumulus clouds over the ocean could compensate for a doubling in atmospheric carbon dioxide, preventing a potentially disastrous planetwide temperature increase. On the other hand, an increase in cirrus clouds could increase global warming.
That clouds represented the weakest element in climate models was illustrated by a study of fourteen such models. Comparing climate forecasts for a world with double the current amount of carbon dioxide, researchers found that the models agreed quite well if clouds were not included. But when clouds were incorporated, a wide range of forecasts was produced. With such discrepancies plaguing the models, scientists could not easily predict how quickly the world’s climate would change, nor could they tell which regions would face dustier droughts or deadlier monsoons.
15.1. The author of the passage is primarily concerned with
(A) confirming a theory
(B) supporting a statement
(C) presenting new information
(D) predicting future discoveries
(E) reconciling discrepant findings
15.2. It can be inferred that one reason the fourteen models described in the passage failed to agree was that
(A) they failed to incorporate the most up-to-date information about the effect of clouds on climate
(B) they were based on faulty information about factors other than clouds that affect climate
(C) they were based on different assumptions about the overall effects of clouds on climate
(D) their originators disagreed about the kinds of forecasts the models should provide
(E) their originators disagreed about the factors other than clouds that should be included in the models
15.3. It can be inferred that the primary purpose of the models included in the study discussed in the second paragraph of the passage was to
(A) predict future changes in the world’s climate
(B) predict the effects of cloud systems on the world’s climate
(C) find a way to prevent a disastrous planetwide temperature increase
(D) assess the percentage of the Earth’s surface covered by cloud systems
(E) estimate by how much the amount of carbon dioxide in the Earth’s atmosphere will increase
15.4. The information in the passage suggests that scientists would have to answer which of the following questions in order to predict the effect of clouds on the warming of the globe?
(A) What kinds of cloud systems will form over the Earth?
(B) How can cloud systems be encouraged to form over the ocean?
(C) What are the causes of the projected planetwide temperature increase?
(D) What proportion of cloud systems are currently composed of cirrus of clouds?
(E) What proportion of the clouds in the atmosphere form over land masses?