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

"And we're considering this in the U.S. It's actually in practice in Europe, and it's based on a couple of notions; first, the notion that it's really too costly and really not needed to eliminate all pollution. The environment can handle some levels, and we look to scientists to tell us what's some acceptable level of pollution, say of carbon emitted to the atmosphere each year. So we set that level and then we in essence say, ok, we're going to sell permits, pollution permits to businesses and others, where the sum of those permits will equal that aggregate level of pollution that's acceptable. And then, furthermore, businesses, if, for example, they find a new technology over time that will allow them to significantly reduce pollution, a business may say, well, I don't need all these permits, and they can sell them back on the open market. So the idea here is that you are selling these permits ultimately to the businesses and others to whom reducing pollution is the most expensive. So you are creating an efficient market, if you will, in pollution. Now, as I said Europe is already doing some version of this, and the U.S. is debating this, and I think we likely will see some type of cap and trade system in the U.S. That's my prediction down the road."