emissions trading
noun /ɪˈmɪʃnz treɪdɪŋ/
  /ɪˈmɪʃnz treɪdɪŋ/
 (also carbon trading)
 [uncountable]- a system that gives countries and organizations the right to produce a particular amount of carbon dioxide and other gases that cause global warming, and allows them to sell this right碳排放权交易;碳交易