Emissions spew out of a large stack at the coal-fired Morgantown Generating Station on the Potomac River in Newburg, Md. Maryland is pushing back against proposals to scale back a cap on emissions from plants in the Northeast. (Photo by Mark Wilson/Getty Images)

Maryland and eight other states that have a regional compact to reduce greenhouse gas emissions have agreed to deeper cuts to carbon emissions over the next decade.

The states participating in the Regional Greenhouse Gas Initiative are pledging to cut emissions from power plants by at least 30 percent between 2020 and 2030. That’s slightly higher than the current agreement to reduce emissions by 2.5 percent annually.

A separate provision would allow for even deeper pollution cuts, if they wouldn’t be too costly to states.

The plan — announced Wednesday — is not yet final, and a meeting is set in Baltimore on Sept. 25 to solicit comment from power companies and others affected by the decision.

Environmentalists and the state of Massachusetts had sought even greater cuts in pollution, pushing for reducing carbon emissions 5 percent a year. But Maryland balkedand threatened to pull out of the pact, saying it would lead to higher energy costs for consumers who are on the same energy grid as coal-heavy states that haven’t signed on to the initiative.

Katie Dykes, a Connecticut regulator who chairs the initiative, said in a statement that the compromise agreement will “secure significant carbon reductions at a reasonable price on into the next decade.”

In addition to Maryland, Massachusetts and Connecticut, the pact includes Delaware, Maine, New Hampshire, New York, Rhode Island and Vermont. New Jersey pulled out of the group in 2011.

“This a strong and environmentally protective approach, it embraces the art of the possible,” Maryland Secretary of the Environment Ben Grumbles said in an interview. “This is a primary example of real progress on climate change.”

The regional initiative, which started in 2009, is a state-driven cap-and-trade system to reduce gas emissions, which contribute to global warming by trapping heat in the atmosphere.

Participating states agree to limit pollution from power plants, and to allow energy producers to bid against each other in auctions for the right to emit carbon. The initiative has raised $2.7 billion from these auctions, money that is being used to fund clean-energy programs.

Environmentalists say such state efforts are especially important since President Trump ’s decision to pull the nation from the global Paris climate pact.

“With the current disastrous policies and rhetoric of the Trump administration, we’re pleased to see these states step up, listen to their constituents, and come together to increase clean energy in the region,” Mark Kresowik of the Sierra Club’s Beyond Coal Campaign said in a statement.

Other advocates praised Maryland Gov. Larry Hogan’s administration for its handling of the regional pact. Hogan (R) has also won praise from environmentalists for supporting a ban on fracking. But he faced some criticism for rolling back regulations meant to reduce pollution in the Chesapeake Bay.

“In this current national political environment, it’s more important than ever for Governor Hogan to take the lead and stand strong with the other states in RGGI,” Karla Raettig, executive director of Maryland League of Conservation Voters, said in a statement.