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　　In the atmosphere, carbon dioxide allows the sun’s rays to enter but prevents the heat from escaping．According to a weather expert’s prediction, the atmosphere will be warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate．If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several meters and severely flooding coastal cities．Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere．

　　In the past, concern about a man－made warming of the earth has concentrated on the Arctic because the Antarctic is much colder and has a much thicker ice sheet．But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming, in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of fuels．Satellite pictures show that large areas of Antarctic ice are already disappearing．The evidence suggests that a warming has taken place．This fits the theory that carbon dioxide warms the earth．

　　However, most of the fuel is burnt in the northern part of the earth, where temperatures seem to be falling．Scientists conclude, therefore, that up to now natural influences on the weather have exceeded those caused by man．The question is：Which natural cause has most effect on the weather?

　　One possibility is the behavior of the sun．Astronomers at one research station have studied the hot spots and “cold” spots, that is, the relatively less hot spots, on the sun．This seems to have a greater effect on the distribution of the earth’s atmospheric pressure, and consequently on wind circulation(循环)．The sun is also variable(可变的)over a long term．Its heat output(输出)goes up and down in cycles．The latest trend being downward is on the way．But that is only a imagination．

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　　You might think that “global warming” means nothing more than a rise in the world’s temperature．But rising sea levels caused by it have resulted in the first evacuation(撤离)of an island nationthe citizens of Tuvalu will have to leave their homeland．

　　During the 20th century, sea level rose 8～12 inches．As a result, Tuvalu has experienced lowland flooding of salt water that has polluted the country’s drinking water．

　　Paani Laupepa, a Tuvaluan government official, reported to the Earth Policy Institute that the nation suffered an unusually high number of fierce storms in the past ten years．Many scientists connect higher surface water temperatures resulting from global warming to greater and more damaging storms．

　　Laupepa expressed dissatisfaction with the United States for refusing to sign the Kyoto Protocol, an international agreement calling for industrialized nations to reduce their greenhouse gas emissions(导致温室效应的气体排放), which are a main cause of global warming．“By refusing to sign the agreement, the US has effectively taken away the freedom of future generations of Tuvaluans to live where their forefathers have lived for thousands of years．”Laupepa told the BBC．

　　Tuvalu has asked Australia and New Zealand to allow the gradual move of its people to both countries．

　　Tuvalu is not the only country that is vulnerable(易受影响的)to rising sea levels．Maumoon Gayoon, president of the Maldives, told the United Nations that global warming has made his country of 311, 000 an “endangered nation”．

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Head above water？

　　TUVALU, a tiny country in the Pacific Ocean, has asked for help as it fears it will be swallowed up by the sea．

　　Storms and huge waves are a constant threat and none of Tuvalu’s nine little islands is more than five metres above sea level．Salt water is already entering the country’s drinking water supply, as well as damaging plants that produce fruit and vegetable．Without urgent help, the country’s days are numbered．

　　But Tuvalu is not the first place to face sinking into the sea．Venice, a historic city in Italy best known for its canals, has sunk about 24 cm over the past 100 years．Experts say that it will have sunk another 20～50 cm by 2050．A century ago, St．Mark’s Square, the lowest point in the city, flooded about nine times a year．Nowadays, it happens more than 100 times．

　　While Venice is slowly sinking into the mud on which it stands, Tuvalu’s rising sea level is caused by global warming．

　　The average global temperature has increased by almost 0．5 centigrade degree over the past century; scientists expect it to rise by an extra 1～3 degrees over the next 100 years．

　　Warmer weather makes glaciers(冰川)melt, adding more water to the ocean．The warmer temperatures also make water expand, so it takes up more space, causing the sea level to rise．The sea level has risen about 10～25 cm in the last 100 years．

　　The main cause of global warming is human pollution．Through burning coal, oil and gas, people have been increasing the greenhouse gases in the atmosphere, such as CO₂．This adds to the power of the greenhouse effect, making the planet even warmer．

　　Many scientists believe that, if the warming is not stopped, there will be huge climate changes．The sea level could rise by one meter this century．

　　Should this come true, millions of homes will be swallowed up by the sea and the world will be flooded with “climate refugees” looking for somewhere to live．

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“I thirst”

　　Each day waterrelated diseases killed 3, 900 of the world’s children

　　Across the world, 1.1 billion people have no access to clean drinking water．More than 2.5 billion people lack basic sanitation．(卫生设备)

　　The combination proves deadly．Each year, diseases related to inadequate(不适当的)water and sanitation kill between 2 and 5 million people and cause an estimated 80 percent of all sicknesses in the developing world．Safe drinking water is a precondition for health and the fight against child death rate, inequality between men and women, and poverty．

　　Consider these facts：

　　●The average distance that women in Africa and Asia walk to collect water is 6 kilometers．

　　●Only 58 percent of children in subSaharan Africa are drinking safe water, and only 37 percent of children in South Asia have access to even a basic toilet．

　　●Each year in India alone, 73 million working days are lost to waterborne diseases．

　　Here are three ways you can help：

　　(1)Write Congress

　　Current(当前的)U．S．foreign aid for drinking water and sanitation budgets only one dollar per year per American citizen．Few members of Congress have ever received a letter from voters about clean drinking water abroad．

　　(2)Sponsor(赞助)a project with a faithbased organization

　　Many U．S．religious groups already sponsor water and sanitation projects, working with partner organizations abroad．Simply put a single project by a U．S．organization can make safe water a reality for thousands of people．

　　(3)Support nonprofit water organizations

　　Numerous U．S．based nonprofits work skillfully abroad in communityled projects related to drinking water and sanitation．Like the sample of nonprofits noted as follows：some organizations are large, other smallscale, some operate worldwide, others are devoted to certain areas in Africa, Asia, or Latin America．Support them generously．

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　　People have smoked cigarettes for a long time now．The tobacco which is used to make cigarettes was first grown in what is now part of the United States．Christopher Columbus, who discovered America, saw the Indians smoking．Soon the dried leaves were transported to Europe．In the late 1800s, the Turks made cigarettes popular．

　　Cigarette smoke contains at least two harmful substances, tar and nicotine．Tar, which forms as the tobacco burns, damages the lungs and therefore affects breathing．Nicotine, which is found in the leaves, causes the heart to beat faster and increases the breathing rate．Nicotine in large can kill a person by stopping a person’s breathing muscles．Smokers usually take in small amounts that the body can quickly break down．

　　Nicotine can make new smokers feel dizzy(头晕)or sick to their stomachs．The heart rate for young smokers increases 2 to 3 beats per minute．Nicotine also lowers skin temperature and reduces blood flow in the legs and feet．It plays an important role in increasing smokers’ risk of heart disease and stroke．

　　Smoking cigarettes is dangerous．Cigarette smoking was the cause of lung cancer and several other deadly diseases．

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　　Behaviors such as smoking, poor eating habits, and physical inactivity(静止)greatly increase a child’s risk of getting cancer in adulthood．For many kids, these and other harmful habits are already well established by the age of 13 years．In America, almost twothirds of cancers could be prevented if these behaviors were never started．The earlier children learn how to prevent illness, the healthier they will be．The ways to make healthy decisions are learned during childhood．It’s far more important to practice a good habit from the beginning than it is to quit an unhealthy one!

　　School health isn’t just about what’s taught in the classroom．It’s about creating policies and programs that increase healthful living．It’s about forcing healthy habits every day and every year when kids are in school．Children’s health and education are harmed by risky behaviors such as using tobacco, and drugs, failure to use seat belts, carrying weapons, lack of physical activity, and poor diet．A good school health program includes：

　　Health education in the classroom．

　　Healthy choices in the school cafeteria(自主餐厅)and vending(自动销售)machines．

　　Physical education that promotes regular exercise, heart fitness, and sun safety．

　　Family and community involvement．