But here, too, change may be afoot.To mimic the advantage ofa carbon tax, many cap-and-trade fans now want governments to auction at leasta share of the permits.

• 为了学习碳排放税的优点，很多“限制排放与交易许可”机制的支持者也希望通过政府拍卖，在许可中分得一杯羹。