Their bill would limit greenhouse gases by requiring polluters to receive or buy emission permits, with the number of available permits - the "cap" in "cap and trade" - gradually falling over time.

他们的提案要求那些温室气体的排放者接受或购买排放许可，可获得的许可的数量将会渐渐减少，以此来限制温室气体。这就是“总量管制与交易制度”的“管制”那一环。

youdao

Moves to do that have been in play for 14 years, and have resulted in nothing to cap the emission rise.

BBC: US and its airlines: Too much hot air?

In his speech, the Arizona senator proposed capping carbon emissions incrementally, with the goal of returning to 1990 emission levels by the year 2020 using a cap-and-trade program.

CNN: McCain appeals to independents with environment pitch

In his speech Monday, the presumed GOP nominee proposed capping carbon emissions incrementally, with the goal of returning to 1990 emission levels by the year 2020 using a cap-and-trade program.

CNN: McCain: Clean energy a 'national security issue'