carbon cap and trade 和 carbon tax 的区别?

Cap-and-Trade—the approach most popular among politicians—would put a quantitative limit on annual carbon emissions by auctioning permits that power plants and other industries would have to purchase in order to burn fossil fuels,whereas,a Carbon Tax—the approach most popular among economists—would discourage emissions reductions by increasing the cost of doing so.
其实我之前也不知道这两个什么意思……不过按这上面的意思就是前者是让大量燃烧化石燃料的单位必须购买相应量的“碳排放许可”以在数量上限制其排放（如由*管理调控各发电厂、工业工厂的排放量并增加其成本）；后者仅仅是在经济的角度上以税收的形式让碳排放的成本增加.(原文可能打错了吧,还是又是我不知道的英语用法……)你要说具体内容的话现在版本太多了,还都千差万别,也只能说大体上是这两点.
区别嘛……现在有很多很多种说法,我比较赞成这种：（前面说两者大部分是相同或相近的,只是对于前者：）
1) there will be some limited trading on a secondary market; and 2) firms can use derivatives to manage their risk.
是说前者在一定程度上限制了中级市场贸易,但是又相对地给了企业管理风险的可能.
我不是这方面的专家……以上只是我自己的理解……有问题的话多包涵……
话说大多数人都支持后者……关于这方面的英文资料很多,随便搜一下就能找到了,有兴趣可以多看看.