For example, the EU demanded that renewables like wind and solar account for 20% of energy supplies by 2020, though this is by no means the cheapest way to cut emissions. In fact, putting up a wind turbine cuts no extra CO2, because total emissions are already capped under the EU-wide carbon-trading scheme.
比方说，欧盟要求到2020年风能及太阳能等可再生能源必须占能源供应的20%，虽然这根本不是最廉价的减排方法。其实安装风力发电机组无法减排多余的二氧化碳，因为全欧盟的碳交易计划已经将总排放量规定死了。其结果是当英国安装一台风力发电设备，葡萄牙和波兰烧煤就变得更便宜了。