The Intent of Cap and Trade
Cap and trade is intended to reduce global warming by reducing the emissions of greenhouse gases. The following material is from "Cap and Trade 101" and was created by the Center for American Progress. It is used with permission.
The cap: Each large-scale emitter, or company, will have a limit on the amount of greenhouse gas that it can emit. The firm must have an "emissions permit" for every ton of carbon dioxide it releases into the atmosphere. These permits set an enforceable limit, or cap, on the amount of greenhouse gas pollution that the company is allowed to emit. Over time, the limits become stricter, allowing less and less pollution, until the ultimate reduction goal is met. This is similar to the cap and trade program enacted by the Clean Air Act of 1990, which reduced the sulfur emissions that cause acid rain, and it met the goals at a much lower cost than industry or government predicted.
The trade: It will be relatively cheaper or easier for some companies to reduce their emissions below their required limit than others. These more efficient companies, who emit less than their allowance, can sell their extra permits to companies that are not able to make reductions as easily. This creates a system that guarantees a set level of overall reductions, while rewarding the most efficient companies and ensuring that the cap can be met at the lowest possible cost to the economy.