If environmental trends in Western nations continue on a positive track, someday children may ask, “Mommy, what was pollution?” But between that day and ours stands the ultimate environmental problem: global warming. Fighting an artificial greenhouse effect is the greatest of environmental challenges, because the cure will not be possible unless almost every nation on Earth participates. In the last century, global temperatures have risen 1 degree Fahrenheit ( 华氏温度 ) Some scientist remain skeptical about projected future warming, but an oft-heard claim, that the idea of global warming is being promoted only by environmental fanatics, is not true. Will global warming cause harm? Some computer models suggest the world might warm by 5 degrees or more during this century, which might be dangerous. Melting polar ice could raise sea levels, while global warming might cause more intense storms and disrupt the weather patterns bring rain to agricultural regions. Computer models are speculative ( 投机的 ), of course, but when the farming areas that we all depend upon for food rely on current temperatures, rolling the dice ( 筛子 ) with the climate cannot be wise. Yet today the United States has no national legislation regulating greenhouse gases. What can we do right now? There are methods to reduce global warming. For instance, individuals can make lifestyle changes. Replace the SUV with a regular car; an SUV that gets 14 miles to the gallon emits 100 tons of greenhouse gases over its lifetime. Check out the new hybrid cars, which get 45 mpg or better. Moderate your use of home heating and air conditioning, most of which is powered by fossil fuels, and upgrade appliances to Energy Star models.