Passage Two Global warming was once an uncommon term used by a few scientists who were growing concerned over the effects of decades of pollution on long-term weather patterns. Today, the idea of global warming is well known, if not well understood. It is not unusual to hear someone complaining about a hot day or a freak storm and remark, "It’s global warming. " Global warming is a significant increase in the Earth’s climatic temperature over a relatively short period of time as a result of the activities of humans. In specific terms, an increase of l or more degrees Celsius in a period of one hundred to two hundred years would be considered global warming. Over the course of a single century, an increase of even 0.4 degrees Celsius would be significant. Most scientists recognize that global warming does seem to be happening, but a few don’t believe that it is anything to be worried about. These scientists say that the Earth is more resistant to climate changes on this scale than we think. Plants and animals will adapt to subtle shifts in weather patterns, and it is unlikely anything catastrophic will happen as a result of global warming. Slightly longer growing seasons, changes in precipitation levels and stronger weather, in their opinion, are not generally disastrous. They also argue that the economic damage caused by cutting down on the emission of greenhouse gases will be far more damaging to humans than any of the effects of global warming. In a way, the scientific consensus may be a moot point. The real power to enact significant change rests in the hands of those who make national and global policy. Some policymakers in the United States are reluctant to propose and enact changes because they feel the costs may outweigh any risks global warming poses. Some common concerns, claims and complaints include: A change in the United States’ policies in emissions and carbon production could result in a loss of jobs; India and China, both of which continue to rely heavily on coal for their main source of energy, will continue to cause environmental problems even if the United States changes its energy policies (critics of these policymakers point out that this approach employs the tu quoque logical fallacy); Since scientific evidence is about probabilities rather than certainties, we can’t be certain that human behavior is contributing to global warming, that our contribution is significant, or that we can do anything to fix it; Technology will find a way to get us out of the global warming mess, so any change in our policies will ultimately be unnecessary and cause more harm than good. What’s the correct answer It can be hard to figure out. Most scientists will tell you that global warming is real and that it is likely to do sonic kind of harm, hut the extent of the problem and the danger posed by its effects are wide open for debate. Though scientists warn that global warming will likely continue for centuries because of the long natural processes involved, there are a few things we can do to decrease the effects. Basically, they all boil down to this: Don’t use as much of the stuff that creates greenhouse gases. On a local level, you can help by using less energy. The electricity that operates many of the devices in our homes comes from a power plant, and most power plants burn fossil fuels to generate that power. Turn off lights when they’re not in use. Take shorter showers to use less hot water. Use a fan instead of an air conditioner on a warm day. Here are some other specific ways you can help decrease greenhouse-gas emissions: Make sure your car is properly tuned up. This allows it to run more efficiently and generate fewer harmful gases; Walk or ride your bike if possible, or carpool on your way to work. Cars burn fossil fuel, so smaller, more fuel-efficient cars emit less CO2, particularly hybrid cars; Turn lights and other appliances off when you’re not using them. Even though a light bulb doesn’t generate greenhouse gas, the power plant that generates the electricity used by the light bulb probably does. Switch from incandescent light bulbs to fluorescent bulbs, which use less energy and last longer; Recycle. Garbage that doesn’t get recycled ends up in a landfill, generating methane. Recycled goods also require less energy to produce than products made from scratch; Plant trees and other plants where you can. Plants take carbon dioxide out of the air and release oxygen. Don’t burn garbage. This releases carbon dioxide and hydrocarbons into the atmosphere. To really stem the emission of greenhouse gases, we need to develop non-fossil fuel energy sources. Hydro-electric power, solar power, hydrogen engines and fuel cells could all create big cuts in greenhouse gases if they were to become more common. At the international level, the Kyoto treaty was written to reduce CO2 and other greenhouse gas emissions worldwide. Thirty-five industrialized nations have committed to reducing their output of those gases to varying degrees. Unfortunately, the United States, the world’s primary producer of greenhouse gases, did not sign the treaty. In March, 2007, former Vice President Al Gore testified in front of Congress and urged them to make some very challenging changes in national policy. These include: Freeze carbon production at the current level and create programs to reduce carbon production by 90 percent by 2050 ; Shift taxation from employment and production to a taxation upon pollution; Create an international treaty that would effectively comply with the Kyoto treaty without carrying the same perceived political baggage; halt the construction of all new coal-based power facilities unless they comply with restrictions on carbon production; increase emission standards across the board for both the automobile industry and power facilities; ban incandescent light bulbs. Gore admits that the decision to enact these and other proposed responses to global warming can be difficult, He also says that climate change is not just a crisis, but the most important crisis mankind has ever faced.The author cited the example of the probable result for the change of policy in the United States (paragraph 5) in order to （）. A．indicate the impact for the alteration in US policy can be severe B．point out the difference in policies adopted in US and that in China and India C．explain why there are obstacles in taking some measures against global warming D．convince the readers it is too expensive to stop the global warming