Senators "could do something like Sen. [Tom] Cotton did with Iran" to send a signal to world leaders that the chamber wouldn't support any deal President Obama negotiates on climate change, a Senate Republican suggested Wednesday.

Sen. Jeff Sessions, R-Ala., was referring to the Arkansas Republican's March letter to Iran's leaders that netted the signatures of 47 senators. The letter warned that any deal Obama struck regarding Iran's nuclear program could be revoked in two years should the next president disagree with the pact.

Republicans had argued the president lacks the authority to come to terms with Iran, though the administration and Democrats contend it's within the purview of the executive branch's abilities to conduct foreign policy.

GOP lawmakers see less of a direct connection between the president's foreign policy powers and any deal Obama might secure at United Nations-hosted climate talks, which begin in late November in Paris. Republicans, such as Senate Majority Leader Mitch McConnell, R-Ky., have issued warnings to world leaders that the GOP-controlled Congress doesn't support a climate deal and have stressed that some of the policies underpinning Obama's climate push — such as a rule regulating carbon emissions from power plants — will face court challenges.

But backing away from a climate deal would be difficult, noted Jeremy Rabkin, George Mason University School of Law professor who nonetheless questioned Obama's ability to act on a climate deal without Senate approval.

"The next administration could certainly say [Obama] made a political commitment, we repudiate it ... Of course, it is an awkward thing to do," he said at an Senate Environment and Public Works Committee hearing.

The White House has discussed using existing treaties to develop a deal that wouldn't require Senate ratification. One system that has gained favor within the administration would call for non-binding national emissions targets while using already approved agreements to establish a legally binding system of reviewing and reporting progress on those commitments.

The legal form of the hoped-for climate pact is unknown. Nations hope to strike an deal that will govern emissions beyond 2020 to keep global temperatures from rising 2 degrees Celsius above pre-industrial levels by the end of the century.

"The idea that we know what the agreement ... there's some speculation about those things, but we really don't know the answer," said Sarah Ladislaw, a senior fellow and director of the energy and national security program with the Center for Strategic and International Studies.

The European Union has advocated for including legally binding emissions cuts because it doesn't think countries will take decisive action without them. Developing countries that bear the brunt of the effects of climate change also want more concrete commitments from post-industrial nations responsible for most of the historical greenhouse gas emissions that many scientists say have contributed to current warming trends.

There is a significant gap between the emissions goal Obama proposed in March and current and planned regulatory actions, said David Bookbinder, a partner at Element VI Consulting and former Sierra Club general counsel.

Obama said the U.S. would reduce economy-wide emissions at least 26 percent below 2005 levels by 2025, but regulatory measures on the books and those scheduled to be undertaken still leave the administration 25-32 percent short of that goal, Bookbinder said. The biggest way to achieve additional emissions reductions would be to regulate agriculture, he said.

But Karl Hausker, a senior fellow in the global climate program at the World Resources Institute, estimated that some effects from regulations — such as technological innovation — and greater gains from energy efficiency would allow the Obama administration to meet its goal.

"The [World Resources Institute] analysis ... looks beyond what's just finalized and near finalized," he said.