[简答题]项目贷款的系统维护需分哪三个阶段来进行，简述每个阶段的维护要点。

{{B}} A Cooler Planet{{/B}}
Scientists are cooking up solutions based on current technology that they say they could dramatically turn down the heat of global warming over the next 50 years.
Innovations such as cheaper wind power, gas-electric hybrid and gas cards that generate funds for climate-change projects already are available. Introducing them across the nation could put a dent in the growth of greenhouse gases that are warming the planet, scientists say.
The concentration of carbon dioxide--a potent greenhouse gas--is likely to double before the end of the century, the United States says. Scientists say further warming is inevitable as greenhouse gas emissions climb but that the worse effects can still be avoided.
"The question now is not ’whether to adapt ’ but ’how to adapt ’" says a 2004 U.N. report on climate change.
The solutions, says experts, must come from action