If pollution continues to increase at the present rate, formation of aerosols in the atmosphere will cause the onset of an ice age in about fifty years’ time. This conclusion, reached by Dr. S. I. Rasool and Dr. S. H. Schneider, of the United States Goddard Space Flight Center, answers the apparently conflicting question of whether an increase in the carbon di- oxide content of the atmosphere will cause the earth to warm up or increasing the aerosol content will cause it to cool down. The Americans have shown conclusively that the aerosol question is dominant.
Two specters haunting conservationists have been the prospect that meddling with the environment might lead to the planet’s becoming unbearably hot or cold. One of these ghosts has now been laid, because it seems that even an increase in the amount of carbon dioxide in the atmosphere to eight times its present value will produce an increase in temperature of only 2(上标)C, which would take place over several thousand years. But the other problem, now looms larger than ever.
Aerosols are collections of small liquid or solid particles dispersed in air or some other medium. The particles are all so tiny that each is composed of only a few hundred atoms. Because of this they can float in the air for a very long time. Perhaps the most commonly experienced aerosol is industrial smog of the kind that plagued London in the 1950s and is an even greater problem in Los Angeles today. These collections of aerosols reflect the sun’s heat and thereby caused the earth to cool.
Dr. Rasool and Dr. Schneider have calculated the exact effect of a dust aerosol layer just above the earth’s surface on the temperature of the planet. As the layer builds up, the present delicate balance between the amount of heat absorbed from the sun and the amount radiated from the earth is disturbed. The aerosol layer not only reflects much of the sun’s light but also transmits the infrared radiation from below almost unimpeded. So, while the heat input to the surface drops, the loss of heat remains high until the planet cools to a new balanced state. Within fifty years, if no steps are taken to curb the spread of aerosols in the atmosphere, a cooling of the earth by as much as 3.5。C seems inevitable. If that lasts for only a few years, it would start another ice age, and because the growing ice caps at each pole would themselves reflect much of the sun’s radiation, it would probably continue to develop even if the aerosol layer were destroyed.
The only bright spot in this gloomy forecast lies in the hope expressed by Dr. Rasool and Dr. Schneider that nuclear power may replace fossil fuels in time to prevent the aerosol content of the atmosphere from becoming critical.
What might avert the danger of the building up of a high concentration of aerosols

A. lingua franca

B. register
C. creole

D. dialect

At the University of Iowa, a student was reported to have the habit of getting up in the middle of the night and walking three-quarters of a mile to the Iowa River. He would take a swim and then go back to his room to bed.
The world’s champion sleepwalker was supposed to have been an Indian, Pandit Ramrakha, who walked sixteen miles along a dangerous road without realizing that he had left his bed. Second in line for the title is probably either a Vienna housewife or a British farmer. The woman did all her shopping on busy streets in her sleep. The farmer, in his sleep, visited a veterinarian miles away.
The leading expert on sleep in America claims that he has never seen a sleepwalker. He is Dr. Nathaniel Kleitman, a physiologist at the University of Chicago. He is said to know more about sleep than any other living man, and during the last thirty-five years has lost a lot of sleep watching people sleep. Says he, "Of course, I know that there are sleepwalkers because I have read about them in the newspapers. But none of my sleepers ever walked, and if I were to advertise for sleepwalkers for an experiment, I doubt that I’d get many takers."
Sleepwalking, nevertheless, is a scientific reality. Like hypnosis, it is one of those dramatic, eerie, awe-inspiring phenomena that sometimes border on the fantastic. It lends itself to controversy and misconceptions. What is certain about sleepwalking is that it is a symptom of emotional disturbance, and that the only way to cure it is to remove the worries and anxieties that cause it. Doctors say that somnambulism is much more common than is generally supposed. Some have estimated that there are four million somnambulists in the United States. Others set the figure even higher. Many sleepwalkers do not seek help and so are never put on record, which means that an accurate count can never be made.
The simplest explanation of sleepwalking is that it is the acting out of a vivid dream. The dream usually comes from guilt, worry, nervousness, or some other emotional conflict. The classic sleepwalker is Shakespeare’s Lady Macbeth. Her nightly wanderings were caused by her guilty conscience at having committed murder. Shakespeare said of her, "The eyes are open but their sense is shut. "
The age-old question is: ls the sleepwalker actually awake or asleep Scientists have decided that he is about half-and-half. Like Lady Macbeth, he has weighty problems on his mind. Dr. Zeida Teplitz, who made a ten-year study of the subject, says, "Some people stay awake all night worrying about their problems. The sleepwalker thrashes them out in his sleep. He is awake in the muscular area, partially asleep in the sensory area." In other words, a person can walk in his sleep, move around, and do other things, but he does not think about what he is doing.
There are many myths about sleepwalkers. One of the most common is the idea that it’s dangerous or even fatal to waken a sleepwalker abruptly. Experts say that the shock suffered by a sleepwalker suddenly awakened is no greater than that suffered in waking up to the noise of an alarm clock. Another mistaken belief is that sleepwalkers are immune to injury. Actually most sleepwalkers trip over rugs or bump their heads on doors at some time or other.