Cap-and-trade means a declining "cap" on total emissions, while allowing trading of pollution permits. Confidence in the certainty of declining caps is based on the mistaken assumption that cap-and trade was proven in the EPA's acid rain program. In fact, addressing acid rain required relatively minor modifications to coal-fired power plants. Reductions were accomplished primarily by a fuel switch to readily available, affordable, low-sulfur coal, along with some additional scrubbing. In contrast, the issues presented by climate change cannot be solved by tweaks to facilities; it requires an energy revolution through investments in building clean-energy facilities.

The biggest obstacle to this revolution is that uncontrolled fossil fuel energy remains much cheaper than clean energy. Cap-and-trade alone will not create confidence that clean energy will become profitable within a known time frame and so will not ignite the huge shift in investment needed to begin the clean-energy revolution. In recent interviews, even the economists who thought up cap-and-trade have said they don't believe it's an appropriate tool for climate change.

What guarantees failure of the proposed climate bills, however, are their provisions for carbon offsets, a concept not used in the acid rain program. Both bills allow all required greenhouse-gas reductions for almost 20 years to be met with carbon offsets rather than actual reductions in use of the capped sources. Offsets -- considered indispensable to keeping cap-and-trade affordable -- are supposed to be "additional" reductions beyond what is legally required. But experience with offsets in Europe and California has shown that ensuring real "additionality" is not an achievable goal.