Since a cap-and-trade system seems increasingly likely in the United States, it's worth asking what the impact might be.
And since you asked, the the Environmental Protection Agency and the Energy Information Agency have an answer. It's not nearly as dire as critics want everyone to believe, and for good reason.
The good news: "Impacts on economic growth are modest. By 2030, cumulative GDP losses range from -0.02 to -0.07 percent across the different scenarios analyzed by EIA and EPA."
The bad news: "Total greenhouse gas emissions in 2030 fall from 9.1 to 9.7 billion metric tons CO2 in the “business-as-usual” case to 6.9 to 7.3 billion metric tons under S.1766 -- a 24 to 26 percent decrease."
Why is that bad news? That estimated cut in greenhouse gas emissions isn't much of a cut compared to current levels of emissions, which totalled 7.1 billion metric tons in 2006. Compare that to Britain, which is debating an 80 percent cut in emissions by 2050.
But I suppose it's a start.