An approach to the control of greenhouse gas emissions, under the Kyoto Protocol, that divides the total permitted quantity of emissions of a particular gas into allowances that grant the holder the right to emit a specified amount of pollution over a given period of time (for example 1 tonne a year). Allowances can be traded but the overall amount remains controlled. At the end of each Commitment Period each holder must surrender sufficient allowances to cover their emissions during that period; if they produce less pollution than they are permitted to, they can trade or sell some of their emissions allowance, but if they produce more pollution they must trade or buy some allowance from another holder. Also known as emissions quota. See also emissions cap.
Subjects: Environmental Science.