The Northeastern states are pushing forward with their plan to create a greenhouse gas cap-and-trade system, minus the region's biggest carbon dioxide emitter, Massachusetts, whose governor backed out of the agreement last year. Late last week, the states released their draft model, including new emissions goals for 2018.

The Regional Greenhouse Gas Initiative (RGGI) aims to cut greenhouse gas emissions throughout the Northeast by setting targets for power plants. Plants that emit less CO2 than their target earn credits that they can sell; those that emit more than their target must purchase credits. The system is similar to one already in place in Europe, and to a private-sector trading market, the Chicago Climate Exchange, that is up and running in the U.S., though still in its early stages.

The new targets released by the states call for lowering emissions to 1990 levels by 2014, and then reducing them another 10 percent by 2018. The plan is now expected to cost residents less than initially thought; the latest figures estimate the cost at between $3 and $16.

Governor Mitt Romney, the Republican governor of Massachusetts, abandoned RGGI last year, saying it would cost too much. Members of the state government hope to pass a bill that would require the state to re-join.

RGGI is in a public comment period until May.

Image credit: RGGI