[, ]a right to send out a measured amount of harmful gases such as carbon dioxide into the air排放单位◆The Kyoto Protocol permits trading of emission units between countries.《京都议定书》允许国家之间买卖排放单位。➡carbon credit Emission units <chn/>Under the Kyoto Protocol, countries are given a number of emission units equal to the maximum amount of harmful gases they are allowed to produce. Countries that produce a smaller amount than their limit can sell units to countries that produce more than their limit. Countries can also earn units, for example by planting trees or helping other countries to use technologies that use energy more efficiently. 《京都议定书》给予各国一定量的排放单位（emission units），等于其被允许排放的有害气体的最大排放量。排放量小于限额的国家可以向排放高于限额的国家出售其排放单位。各国也可以通过植树或帮助别国采用可提高能源使用效率的技术等方式获取排放单位。All units are the same size and can be traded in the same way. But some people distinguish units that are earned from those that are given by calling them carboncredits or emissioncredits rather than emissionunits. 所有的排放单位的大小相同，可以用同样的方式进行交易。然而有些人把获取的单位和分配的单位区别开来，称为碳信用额（carbon credits）或排放配额（emission credits），而不是统称为排放单位（emission units）。Emission credit is also used to describe the units of systems other than the Kyoto Protocol, for example the system in the US to reduce sulphur dioxide pollution. * emission credit （排放配额）还用来指《京都议定书》以外的度量制度，例如美国降低二氧化硫污染的制度。