It may take another year or two, but the federal government is getting closer to embracing climate change policy such as a cap and trade system on carbon emissions, which would monumentally change the global economy, and hopefully, peel back the already visible effects of global warming, said Vicki Arroyo, the director of policy for the Pew Center on Global Climate Change, in Arlington, Va.

Arroyo spoke on climate change and policy yesterday at the University of Rhode Island’s Graduate School of Oceanography as part of a week-long lecture series sponsored by the Metcalf Institute for Marine and Environment Reporting, a nonprofit organization that works to bridge the communication gap between scientists and the public.

Arroyo, who was at the U.S. Senate last week for the demise of the Boxer-Lieberman-Warner bill, said — despite witnessing the Republican opposition to ask clerks to read aloud the 492-page bill and the failure of supporters to hold a debate — she is optimistic that Congress will act soon to regulate greenhouse gases.

The science proving climate change is no longer widely debated, she said. More than 110 hearings have been held on the issue this session, about 150 bills mention it and Congress is hearing testimony from credible scientists, she said.

“A year or two before that we were hearing from … Michael Crichton [author of Jurassic Park],” Arroyo said, “because that is who [Oklahoma Sen. James] Inhofe invited to testify on the EPW [Environment and Public Works] panel. This is really a sea change.”

If the United States adopted a cap and trade program, the government would set a limit on greenhouse gas emissions, and auction or give away emission credits to large polluters while systematically lowering that limit until the goal of the 80-percent reduction of 1990 levels is reached around 2050. Firms that can cut emissions cheaper than others can sell their credits, presumably bringing the total level of emissions down.

In addition to the change of culture in Washington, Arroyo said, a feeling of inevitability among many companies and presidential candidates who both support cap and trade, and the prospects for requiring cuts in carbon emissions look even better. Forty-two companies, including giants DuPont and General Electric, have joined Pew, a nonprofit, nonpartisan research group, in the U.S. Climate Action Partnership to advocate to lawmakers for climate change laws.

States, including Rhode Island, are pushing the issue as well.

By taking on two measures intended to address global warming — the Regional Greenhouse Gas Initiative, and a renewable energy goal of 16 percent by 2020 — Rhode Island and other states are creating pressure on the federal government to act.

State lawmakers have introduced a bill in both chambers to reduce greenhouse gas emissions by 80 percent by 2050, the same as the national target and the benchmark believed to avoid the worst effects of climate change.

Yesterday, alongside environmental groups, energy-provider National Grid, Attorney General Patrick C. Lynch and Providence Mayor David N. Cicilline announced their support for the Climate Solution Acts, both of which are still in committee.

One major incentive to pass the legislation this year — besides that it does not request funding — is to be at the front of the line to apply for possible federal dollars, said Cynthia Giles, director of the state chapter of the Conservation Law Foundation.

“I think that it is very encouraging that these prominent community leaders are throwing their weight behind this bill,” Giles said. “Not only does it address climate change, it helps Rhode Island economically.”

The legislation calls for the state to establish a greenhouse gas cap, take an inventory of the emissions produced by the state and a group of stakeholders to make recommendations about how the goal should be met.

More than 15 other states, including all of New England, New York and New Jersey, have set greenhouse gas reduction targets, and more than half of all states have set mandatory goals for renewable energy generation.

Those who oppose capping carbon emissions say the measures will be too expensive and the costs will ultimately fall on the public.

ngarcia@projo.com