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Global warming
On Feb. 2, 2007, the United Nations scientific panel studying climate change declared that the evidence of a warming trend is "unequivocal," and that human activity has "very likely" been the driving force in that change over the last 50 years. The last report by the group, the Intergovernmental Panel on Climate Change, in 2001, had found that humanity had "likely" played a role.
The addition of that single word "very" did more than reflect mounting scientific evidence that the release of carbon dioxide and other heat-trapping gases from smokestacks, tailpipes and burning forests has played a central role in raising the average surface temperature of the earth by more than 1 degree Fahrenheit since 1900. It also added new momentum to a debate that now seems centered less over whether humans are warming the planet, but instead over what to do about it. In recent months, business groups have banded together to make unprecedented calls for federal regulation of greenhouse gases. The subject had a redcarpet moment when former Vice President Al Gore's documentary, "An Inconvenient Truth," was awarded an Oscar; and the Supreme Court made its first global warming-related decision, ruling 5 to 4 that the Environmental Protection Agency had not justified its position that it was not authorized to regulate carbon dioxide.
The greenhouse effect has been part of the earths workings since its earliest days. Gases like carbon dioxide and methane allow sunlight to reach the earth, but prevent some of the resulting heat from radiating back out into space. Without the greenhouse effect, the planet would never have warmed enough to allow life to form. But as ever larger amounts of carbon dioxide have been released along with the development of industrial economies, the atmosphere has grown warmer at an accelerating rate: Since 1970, temperatures have gone up at nearly three times the average for the 20th century.
The latest report from the climate panel predicted that the global climate is likely to rise between 3.5 and 8 degrees Fahrenheit if the carbon dioxide concentration in the atmosphere reaches twice the level of 1750. By 2100, sea levels are likely to rise between 7 to 23 inches, it said, and the changes now underway will continue for centuries to come.
参考译文：
全球变暖
2007年2月2日，联合国研究气候变化的科学小组称，全球变暖的趋势已是毋庸置疑，并且，在这过去的50年中，人类的活动极有可能是这一变化的始作俑者。美国政府气象变化研究小组2001年的最后一篇报告就已经表明了，人类的活动可能扮演这一破坏性角色。
单单增加的极其这个词，不仅仅反映了科学证据的逐步增加--诸如，从烟囱和管道排放出来的二氧化碳和其他可导致温室效应的气体，以及烧毁森林，都是致使地球表面平均温度从1900年以来上升1华氏摄氏度以上的重要原因--而且，还为现如今人类的主要工作从以讨论全球变暖是不是人类所导致为中心，转向探讨如何对付全球变暖提供了新的推动力。在最近几个月，大的商业集团首次联合起来呼吁制定控制温室气体的联邦政府规则，这个呼吁在美国前副总统戈尔的记录片《难以忽视的真相》获得奥斯卡奖后得到了非常热烈的响应。最高法院以5比4作出了他们第一个关于全球变暖的裁决，但环境保护署没有证明它未授权规范二氧化碳的立场。
从最早期开始，温室效应一直是地球运转方式的一部分。二氧化碳和甲烷之类的气体致使太阳光可以到达地球，也将一部分产生的热量反射回太空。没有温室效应，地球就不可能变得足够的温暖以使生命形成。但是，随着工业经济的发展，越来越多的二氧化碳被释放，大气正在变得越来越热，从1970年以来气温的上升幅度是20世纪平均增幅的三倍。
气象小组最近的预计报告表示，如果二氧化碳浓度达到工业化之前水平的两倍，气候将很可能上升3.5到8华氏摄氏度。到2100年，海平面很有可能上升7到23英寸，并且据称，这种正在发生着的变化还将持续几个世纪。
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