The retirement of Senate Environment and Public Works Chairman Thomas R. Carper, D-Del., will leave a vacancy on the committee where he shepherded laws to address greenhouse gas emissions.

Carper, 76, announced on Monday that he would not seek a fifth term but instead hoped to focus on what he could accomplish during his final 20 months in office.

Carper’s departure would create a vacancy for the top Democratic slot on the Environment and Public Works Committee. Next in line for Carper’s committee seat would be Senate Budget Chairman Sheldon Whitehouse, D-R.I., assuming Sen. Bernie Sanders, I-Vt., wants to retain his chairmanship of the Health, Education, Labor and Pensions Committee if he runs and wins reelection next year.

A Whitehouse move would likely elevate Sen. Jeff Merkley, D-Ore., to the top Democratic seat on the Budget Committee, since more senior Democrats on that panel already head other committees. As chairman of that committee, Whitehouse has held hearings examining the impact of climate change on the budget and financial system.

On a call with reporters on Monday, Whitehouse said he has made “no decision” on whether he would seek the Environment and Public Works chairmanship in 2025.

Whitehouse said that noteworthy among Carper’s accomplishments is the fee included in last year’s climate, tax and health care law, which will in time charge up to $1,500 per ton on methane emissions from oil and gas companies, pipeline operators and others.

Methane is more potent at trapping heat in the atmosphere than carbon dioxide in the short term, but groups such as the U.N. Environment Programme have found that addressing methane emissions can help ensure the world reaches targets set under the Paris Agreement.

“I think there’s nobody else who could have had the conversation with [West Virginia Democratic Sen.] Joe Manchin that he did to get that first pollution fee passed into law,” said Whitehouse. “And I think once the Biden administration starts implementing it vigorously, we’ll see what a big difference it makes.”

Sen. Edward J. Markey, D-Mass., another member of the committee, also pointed to the methane fee and another provision in last year’s law that established the EPA’s Greenhouse Gas Reduction Fund, which provides capital to renewable energy projects.

Environmental groups such as Evergreen Action and the League of Conservation voters applauded Carper’s work on the bipartisan infrastructure law as well as his work to address hydrofluorocarbons, which are also potent greenhouse gases. With Sen. John Kennedy, R-La., Carper introduced a bill to phase down the production and consumption of HFCs that was included in the fiscal 2021 appropriations law.

Carper led the successful effort to ratify the Kigali Amendment to the Montreal Protocol last September, which also calls for the phasing down of HFCs. In his retirement speech, Carper outlined the issues he hopes to focus on during his final months in office, which includes legislation to address global warming and the deployment of clean energy technologies.

“For example, we need to chart a bipartisan path forward on permitting legislation that accelerates the deployment of clean energy projects to help us meet our climate change goals, and to create jobs while adhering to the basic bedrock environmental laws of our country and maintaining protection for environmental justice communities,” said Carper.

Carper and Sen. Brian Schatz, D-Hawaii, last week introduced a discussion draft for their permitting proposal.

David Lerman contributed to this report.