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1、wordUnit 22Lesson 1 Global WarmingCan we take the heat?In the last few decades, scientists have reached consensus and reported that human beings are causing changes in the Earths climate something previously seen as beyond our control. They claim that in the last 50 years, gases pumped into the Eart
2、hs atmosphere by the factories and vehicles have been speeding up the process of global warming and affecting our climate. Looking ahead, scientists believe that global warming could be one of the biggest environmental problems facing the 21st century. But what exactly is global warming, why is it s
3、een as a danger, and how is it relevant to our lives?Global warming refers to an average increase in the Earths temperature that, in turn, leads to climate change. Scientists found that the temperature of the Earth is controlled by greenhouse gases such as carbon dioxide which trap heat from the sun
4、 in the Earths atmosphere. Without these naturally occurring gases, the suns rays would bounce back into space leaving the Earth cold and impossible to live on. When the presence of these gases in the atmosphere increase, however, more heat is trapped and the Earths temperature rises.Over the last 1
5、00 years, the global average temperature has increased by 1F and many experts insist that the blame for this global warming can mostly be pinned on human activities. As a result of increased industry, agriculture, the cutting down of forests, the increase in transport and the burning of fuels, nearl
6、y 6 tonnes of carbon dioxide goes into the atmosphere every year for every one of the Earths 6 billion people. The amount of carbon dioxide in the atmosphere has risen by more than 30% in the last 250 years with half of this increase occurring since 1960. Given this data, it seems that the link betw
7、een human activities and rising global temperatures is not merely a coincidence.A temperature increase of 1F may not sound like a lot, but if we continue to produce carbon dioxide and other gases in such huge quantities, we are condemning life on Earth and should expect severe consequences. Recent r
8、eports warned that global warming will cause terrible climate changes including more frequent flooding, heat waves and droughts. Serious diseases will spread and industries that rely on nature such as fishing will be badly affected. Increased temperatures will also cause the polar ice to melt, raisi
9、ng sea levels and flooding many islands and cities. How can we stop these disasters from happening?Governments all over the world have a responsibility to reduce the amount of carbon dioxide which their countries are producing. If less carbon dioxide goes into the atmosphere, global warming will slo
10、w down. This is no easy task, however, and some governments, for example, the USAs federal government, express reservations about whether global warming is really caused by human activities.Many people believe that they are simply not prepared to sacrifice the amount of money they make from industry
11、 to save the Earth. But why wait around for governments to take action? Experts advocate that each person play their part. They suggest making small changes like taking public transport, recycling, using low-flow shower heads, and buying light bulbs that use less energy. Even simple things like usin
12、g recycled paper or switching off the lights when you leave a room can help. If we add up all these small changes made by everyone worldwide, they wont be such small changes. They could be the changes that save our future. After all, theres no substitute for our Earth. Its all weve got to live on.Un
13、it 22 Lesson 3 Natural DisastersNature is turning on usThe last few years have seen environmental disasters on a grand scale, and experts are predicting far worse to e. Jin Li reports on our Earths changeable weather patterns.In the last decade, thunderstorms, floods, earthquakes, typhoons, volcanic
14、 eruptions, tsunamis and forest fires have bee increasingly mon.There has been terrible flooding in Asia, Africa,America and Oceania. (1) _ Storms have been getting worse everywhere too, with a growing number of hurricanes hitting the US, and Central America. Reduced rainfall has affected large area
15、s of Africa for years leaving irrigation canals dry and many other zones are being drier. (2) _ A number of nations have already been in armed conflict over water, and reduced rainfall in the west of the US has resulted in huge forest fires.Volcanic eruptions and earthquakes have always been a threa
16、t in certain parts of the world. A volcanic eruption nearly wiped out the small island of Montserrat in 1997, and there have been serious earthquakes in many parts of Asia, Europe and South America. In the last three years, Indonesia has had a rough time, suffering several killer quakes and it is still recovering from the Asian tsunami caused by an offshore earthquake on De
