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 planet-wide temperature increase? D. What proportion of cloud systems are currently composed of cirrus clouds? E. What proportion of the clouds in the atmosphere form over land masses?