Global warming is defined as an increase in the average temperature of the earth’s atmosphere. （背景导入可以采用下定义的方式。）This trend began in the middle of the 20th century and is one of the major environmental concerns of scientists and governmental officials worldwide（注意用法及位置）. The changes in temperature result mostly from the effect of increased concentrations of greenhouse gasses in the atmosphere（如何地道地表达全球气候变暖的原因）. These gasses, which include carbon dioxide and methane（沼气）, are mostly produced through human activity.
Global Warming Debate Controversy
The global warming debate has quickly become a source of controversy. People disagree on how to address the problem and some simply do not believe that global warming is even occurring at all. Global warming is an internationally recognized problem and many nations are on board with（与。。。一起） addressing the issue in the most effective manner possible（注意最高级的表达）. The Kyoto Agreement was called for a reduction in greenhouse gas emissions and, as of November 2009, was signed by 187 nations.（注意积累例子，京都议定书） Since 1750, there has been an overall increase of 90-250 percent in the release of carbon dioxide.
If global warming continues at the rate it is right now, scientists warn against a large number of ill effects（负面影响）.注意学习下面作者的线性推理，积累各种导致结果的搭配。 Decreases in the amounts of ice and snow in some regions have already endangered many species and continue to do so. Further global warming will also result in a melting of the polar ice caps, which is already occurring. This will lead not only to loss of habitats, but also to a rise in the level of the ocean. A rise in ocean levels could bury some of the coastal cities and islands under miles of water and greatly reduce the amount of land available for human life.
Climate change already impacts a large number of species.平时注意积累事例，在考场上信手拈来。 For example, coral reefs and mangrove trees have declined in numbers. There is also significant evidence to support changes in forestry森林 over the last 100 years. As global warming has sped up, there have been a number of responses, both innate and planned. Many animal species have responded by migrating to cooler climates. Others have adapted and some are simply close to extinction.
Political & Scientific Reaction
As far as politics go, the responses are just as varied. Mitigation is common and calls for a reduction of emissions and less reliance on fossil fuels（注意积累解决方案）. Coal burning power plants are now replaced with hydraulic power plants（水电站） and electrical cars are replacing some gasoline efficient cars. （积累例子。）Many people, however, feel that this is not enough. These “environmental radicals激进分子” want to see a complete overhaul of the system and severe reduction of any reliance on factories or machines that produce greenhouse gasses. Some environmental radicals have proposed a system called geo-engineering. This would involve engineering the climate of the earth artificially through removing carbon dioxide from the atmosphere or blocking incoming sunlight. These techniques would be particularly costly to develop, so they are strongly opposed by supporters of mediation and simple policy change.
When it comes down to it, most politicians and scientists agree that the power to stop global warming lies mostly with the people. Whether a supporter of simple mediation and reduction of use or a believer in dramatic overhauls such as geo-engineering, most scientists agree that the more people who are on board, the better. One survey found that over one-third of people were completely unaware of global warming and its effects. A great first step toward changing the environment would be to educate these people.