degrees Fahrenheit. Scientists believe it's human activity that's driving the temperatures up, a process

Transcription

1 Global Warming For 2.5 million years, the earth's climate has fluctuated, cycling from ice ages to warmer periods. But in the last century, the planet's temperature has risen unusually fast, about 1.2 to 1.4 degrees Fahrenheit. Scientists believe it's human activity that's driving the temperatures up, a process known as global warming. Ever since the industrial revolution began, factories, power plants and eventually cars have burnt fossil fuels such as oil and coal, releasing huge amounts of carbon dioxide and other gases into the atmosphere. These greenhouse gases trap heat near the earth through a naturally-occurring process called the greenhouse effect. The greenhouse effect begins with the sun and the energy it radiates to the earth. The earth and the atmosphere absorb some of this energy while the rest is radiated back into space. Naturallyoccurring gases in the atmosphere trap some of this energy and reflect it back, warming the earth. Scientists now believe that the greenhouse effect is being intensified by the extra greenhouse gases that humans have released. Evidence for global warming includes a recent string of very warm years. Scientists report that 1998 was the warmest year in measured history with 2005 coming in second. Meanwhile, readings taken from ice core show that the greenhouse gases carbon dioxide and methane have hit their highest levels in the past 420,000 years. Arctic sea ice is also shrinking. According to NASA studies, the extent of Arctic sea ice has declined about 10% in the last thirty years. As long as industrialised nations consume energy and developing countries increase their fossil fuel consumption, the concentration of greenhouse gases in the atmosphere will continue to rise. Researchers predict that temperatures will increase about 2 f to 10 f by the end of the 21 st century. What's less certain is what rising temperatures mean for the planet. Some climate models predict subtle changes, others forecast rising sea levels which could flood coastal areas around the world. Weather patterns could change, making hurricanes more frequent. Severe droughts could become more common in warm areas, and species unable to adapt to the changing conditions would face extinction. Although much remains to be learnt about global warming, many organisations advocate cutting greenhouse gas emissions to reduce the impact of global warming. Consumers can help by saving energy around the house, switching to compact fluorescent light bulbs and driving fewer miles in the car each week. These simple changes may help keep the earth cooler in the future. National Geographic video,

2 Global Warming National Geographic video, 2008 WORKSHEET I. Vocabulary A. Scan the text for words or expressions related to global warming. Underline them. B. Now classify these words and expressions below in the left column. Give their definition in the right column, as well as an example in a sentence taken from the text or the dictionary. (You can use the dictionary section of this website: II. Present perfect

3 Scan the text and find 5 sentences in the present perfect. 1. Explain why the present perfect was used in each of them. 2. Explain why for et since were used. If you need help with the present perfect, you can use the grammar section of this website : 1. For 2.5 million years, the earth's climate has fluctuated. III. Expressing probability 1. Read the text again and highlight modal auxiliaries. 2. Translate the sentences where these modal auxiliaries appear. 3. What do these modal auxiliaries express? 4. What is the structure of a verb group with a modal auxiliary? Classify the following modal auxiliaries on the probability scale (MAY, MIGHT, WILL, COULD, CAN'T) 100% 50% 25% 0-10%

4 CO2 in Grenoble, tons/year IV. Graph description 1. Find synonyms for these two words in the text and in your vocabulary : to increase =... to decrease =... Find in the text the word you would use to describe a series of increases and decreases : Complete the graph with the right verbs from the list, following the example : to rise, to fall, to level off, to fluctuate, to go up, to stabilize, to plummet, to rocket, to hit (its) highest levels, to reach a peak, to soar, to go down, to increase, to decrease, to decline. 3. You can use a thesaurus to complete your list. Use > dictionaries) to go up 3. You can use adverbs with those verbs to describe the trend in more details: slightly = a little, slowly dramatically, sharply = a lot gradually, steadily = regularly Use those adverbs with a verb to complete the vocabulary. Ex : to plummet = to decrease dramatically There are also a few nouns to describe trends : an increase a rise a fall a decrease

5 Pay attention to prepositions : to level off/stabilize at 3 tons/year. to reach a peak of 15 tons/year. 3. Use this new vocabulary to describe the graph above (III.2).

6 4. Now describe and analyse the following graph. Pay attention to units and scales!