Dr. Mike Walden, North Carolina Cooperative Extension economist in the College of Agriculture and Life Sciences at N.C. State University, responds:

"Well, the cap part is, first, that some group - of scientists, probably - will decide how much carbon-based fuel is safe to use collectively in the country. And that will be the cap. That will say we can't use more than this amount of carbon-based fuel in any given year. Then the government will take that total amount, divide it up into little chunks, if you will, and sell permits. Each permit will allow a company, for example, to emit that amount of pollution based on their use of carbon-based fuel. The trade part will come in over time, where companies may say, 'Well, gosh, instead of buying these permits, what we're going to do is try to reduce our use of carbon-based fuels. We're going to go to alternatives, therefore, we don't need to own these permits that we have. We're going to sell them, and we'll sell them to other companies that may have a difficult time converting to non-traditional types of fuel.' And so that's the trade part. And that can go on over many, many different years. Now in terms of what the government will do with the money that they will raise by selling these permits, they could do a couple of things. They could use it to fund research on energy alternatives. They could use it to implement those new technologies, or they could use it to fund tax cuts to individuals and to companies."