Directions: Read the text and choose the most suitable heading from this list for each paragraph of the text.
A. Possible problems due to global warming B. Warmer summer in Dallas C. Help from Methane D. One important step E. Getting warmer and warmer in some places F. Problems bigger than benefits |
76.__________
Here is what global warming could do in a few years: in Dallas, a doubled level of carbon dioxide would increase the number of days a year with temperatures above 100 degrees from nineteen to seven-eight. On sixty-eight days, as opposed to the current four, the temperature wouldn’t fall below 80 degrees at night. One hundred and sixty-two days a year, the temperature would top 90 degrees.
77. __________
Although most scientists agree that increasing levels of carbon dioxide and other greenhouse gases will inevitably lead to global warming, no one is certain how fast and how much temperatures will rise and what the effects will be in any geographical areas. This gives policymakers an excuse for delaying action. Some experts predict that within two centuries glaciers(冰川) in the North and South Poles will melt, ocean levels will rise, and much of what is now the coast of the United States will be under water. They also predict great droughts and hurricanes, as a result of climate changes.
78. __________
Other scientists think the changes will be much more gradual, even beneficial. After all, Canada would not complain if the productive corn-growing lands were shifted north. While many nations could end up with milder climates, the change-perhaps 100 times faster than at any time in human history—could be so drastic(猛烈的) that many of the benefits would be lost. There could be crowds of environmental refugees, as well, making the tragedy of the Dust Bowl era seem mild in comparison.
79. __________
What can we do? Humanity’s contribution to the greenhouse effect comes from so many basic activities that we can’t hope to eliminate it completely. Some steps have already been taken. Since the 1970’s, the use of CFCs as aerosol-can propellants(喷雾器) has seen banned in the United States.
80. __________
Another strategy is to burn as much as methane(甲烷) as possible. This aids CO2 to the air, but since methane traps twenty times as much heat as CO2, the net result is worth-while. The gas in many garbage landfills is already being used in a number of places around the United States. It is being used to heat thousands of homes.
Section D