President Obama can deliver on his international carbon-reduction commitments without new congressional action by making full use of his authority under the Clean Air Act and other laws, according to the head of a prominent environmental think tank.

Armond Cohen, executive director of the Clean Air Task Force (CATF), said in an open letter to the president released today that Obama's pledge of reducing heat-trapping emissions 17 percent by 2020 and 80 percent by midcentury is already within reach.

"The U.S. currently is within striking distance of the 2020 goal for carbon dioxide," Cohen said.

A combination of economic and market trends, together with rules put forward during Obama's first term, has put the United States on track to come very close to its 2020 target, reducing emissions by 16.3 percent below 2005 levels, according to a report released in October by the Washington-based think tank Resources for the Future. The estimate assumes U.S. EPA will finalize proposed rules for new power plants and write sufficiently stringent Clean Air Act requirements for the existing plants.

But EPA could hit the target by adding a methane rule for oil and gas production, Cohen writes. Some recent studies have placed the methane leakage rate for gas production much higher than a previous estimate of 2.3 percent of production. The Environmental Defense Fund is facilitating a study that seeks to firm up those estimates, and its results are due out this spring.

CATF is not the only environmental group that has begun to push for a rule designed to limit methane from oil and gas production, arguing that leakage of the powerful greenhouse gas subtracts from the climate change benefits of utilizing more gas instead of coal in electric generation.

While EPA finalized a rule last April that requires new hydraulically fractured gas wells to use technology that will cut toxic emissions by capturing vented natural gas, environmentalists say a more targeted methane rule would yield better results, and the cost could be offset when captured natural gas was sold.

But in an interview this week, American Petroleum Institute regulatory head Howard Feldman noted that EPA touted the rule's methane co-benefits when it was released.

"Nobody was saying it was a methane rule," he said. "But that's effectively what it is."

Obama's 2050 target will be harder to reach, requiring the development and deployment of new technologies.

"Abundant natural gas, while less carbon intensive than coal, is not a long run climate solution," Cohen wrote.

U.S. utilities that run on natural gas will have to employ carbon capture and storage technologies, just as new coal-fired power plants are required to do under a greenhouse gas rule EPA is expected to finalize this year.

To promote next-generation nuclear power, larger-scale renewable energy projects and other zero-carbon technologies, Cohen suggested that Obama promote Department of Energy programs to provide research and development and make several other policy changes, including streamlining the Nuclear Regulatory Commission's licensing procedures to encourage investment in advanced nuclear energy.

He also noted that the president pledged in the aftermath of his re-election that he would initiate a "conversation" with innovators on ways to address climate change. The Council on Environmental Quality is said to be considering several ways of making good on that promise, including a possible White House summit on climate change.

"Mr. President, let's begin that conversation right now," Cohen wrote.