Nine Northeast and Mid-Atlantic U.S. states are reducing by almost half the amount of carbon dioxide power plants are allowed to emit.

The Regional Greenhouse Gas Initiative, the United States' first market-based regulatory program to reduce greenhouse gas emissions, announced Thursday it would lower the 2014 emissions cap from 165 million tons to 91 million tons.

Last year, power plants in the nine states emitted about 91 tons of carbon dioxide despite the 165 million-ton cap, mostly because of the region's growing dependence on natural gas.

RGGI projects that emission allowances under the updated cap-and-trade scheme will increase in price from $4 in 2014 to $10 by 2020. An allowance allows the owner to emit 1 ton of carbon dioxide.

While power plant operators typically pass the cost of the allowances on to consumers via higher electricity prices, RGGI maintains that it expects customer bills to increase just 1 percent.

The states in RGGI, launched in 2009, are: Connecticut, Delaware, Maine, Maryland, Massachusetts, New Hampshire, New York, Rhode Island and Vermont.

New Jersey was a member until May 2011. In announcing his state's withdrawal from RGGI, Gov. Chris Christie at that time said the regional climate initiative "does nothing more than tax electricity, tax our citizens, tax our businesses, with no discernible or measurable impact upon our environment."

But Dale Bryk, director of the Energy and Transportation Program at the Natural Resources Defense Council, suggested that other states look to RGGI as a model, particularly as the Environmental Protection Agency prepares to issue carbon pollution standards for existing power plants nationwide.

"This program has shown the nation unequivocally that environmental and economic progress can indeed go hand in hand," Bryk said in a statement Thursday.

A Duke University poll released this week indicates that although 64 percent of Americans asked said they "strongly" or "somewhat" support regulating greenhouse gas emissions from power plants, factories and cars, support for cap-and-trade is around 30 percent.

"The survey shows strikingly high numbers of Americans accept that the climate is changing, but support for market-based approaches such as a carbon tax and a system of tradeable emissions are not popular among survey respondents," said Sarah Adair, co-author and associate in research at Duke's Nicholas Institute for Environmental Policy Solutions.

"Support rises when asked about more familiar concepts of regulation, such as performance standards, but respondents appear to have little or no knowledge about the possible use of a cap-and-trade system to address climate change," Adair said.