The election of President Obama, coupled with increases in the margins of control held by Democrats in both the House and the Senate, made sweeping climate legislation seem like a sure thing. And the House did go on to pass the Waxman-Markey cap-and-trade bill.

However, ensuing voter backlash to a bill that would raise energy costs and tax the economy in the middle of a deep recession slowed the momentum for equivalent Senate action. Then along came last winter's "climategate" scandal, which severely eroded public confidence in the global-warming science that supposedly justifies climate legislation.

Why are global-warming bills and similar measures so unpopular? Because they cost so much and help so little. The Center for Data Analysis at The Heritage Foundation found that the aggregate lost national income (GDP) from the Waxman-Markey bill would be more than $9 trillion for just the first two dozen years of a 40-year program. That adds up to thousands of dollars per year per family -- and leads to energy price increases of 50 percent to 90 percent.

Even using the questionable Intergovernmental Panel on Climate Change's estimates of temperature change, this sacrifice would moderate temperatures by theoretical but unmeasurable thousandths of a degree by 2050 -- and, at most, tenths of a degree by the end of the century.

One of the reasons there is so little impact, even in theory: The developing world wants to keep developing, which requires more energy. China recently passed the United States as the largest total emitter of carbon dioxide and is projected to have double our emissions within several years. Starting at even lower per-capita levels than China, other developing countries, such as India and Brazil, will be large emitters as they too strive for economic growth. The projected growth in emissions from these countries dwarfs our cuts under cap and trade, rendering such policies futile as well as expensive.

Seeing the unattractive tradeoff such legislation presents, sponsors started claiming their legislation stimulates instead of stifles the economy. It is almost humorous to see how the titles of nearly identical pieces of legislation have changed.

The Senate bill, S. 2191, started as "Lieberman-Warner Climate Security Act of 2007." A little more than one year later, Waxman and Markey didn't even mention climate in their "Clean Energy and Security Act of 2009." When the polls clearly showed that people didn't like the idea of losing millions of jobs for thousandths of a degree, Sens. John Kerry and Barbara Boxer called their bill the "Clean Energy Jobs and American Power Act."

But changing titles cannot change the economics of the policies. Capping CO2 will cut energy to the American economy, and this will hinder economic growth. This is not just the conclusion of conservative economists. The Brookings Institution's analysis of generic cap-and-trade measures shows how it stunts GDP. Obama's own EPA and Department of Energy, along with the Congressional Budget Office, show negative impacts on the economy in their analysis of the cap-and-trade bills.

The unbalanced cost-benefit relationship makes climate legislation fundamentally unappealing. That is why the Senate is having so much trouble passing cap-and-trade. Voters don't want it.

Moreover, the equations don't hold out much hope for compromising on scaled-down legislation. Giving up $100 to get $1 is a bad idea that doesn't get better by saying, "We will start by trading a dollar for a penny." The tradeoff just doesn't make sense.

For now, it seems, climate legislation in the Senate is blocked by understandable voter opposition. But the lame-duck session following the elections may unleash the same special-interest feeding frenzy that led to the passage of Waxman-Markey in the House a year ago. Stay tuned.