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Earth was warmed by about 1degree F over the past 100 years.Scientists are not exactly sure why and how.The Earth could be getting warmer on its own, but many of the world's leading climate scientists think that things people do are helping to make Earth warmer.Scientists are sure about the greenhouse effect.The greenhouse effect is the rise of temperature that the Earth experiences because certain gases in the atmosphere (water, vapor,carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun.Without these gases heat would escape back into space and Earth's average temperature would be about 60 degrees F colder.Because of how they warm our world , these gases are referred to as 'greenhouse gases'.Scientists know that the greenhouse gases make the Earth warmer by trapping and reflecting energy back to the Earth.Global warming refers to an avarage increase in the Earth's temperature, which in turn causes changes in climate.A warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans.Scintists are concerned about global warming caused by human activites.Gases from factories, cars, and forest fires may contribute to global warming.The problem could be controlled by reducing vehicle emissions and limiting the gases released from power stations. ( People and Nature)
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