Life in the Obama Administration means facing up to two facts. First, climate change is no typical “legacy issue,” of the sort that preoccupy second-term presidents. It’s one of the greatest threats humanity has ever faced. Second, congressional Republicans could really care less, and even if they acknowledge that the problem exists, they’ll use every means at their disposal to stifle any attempt to address it. To navigate this dilemma, the New York Times reports, the White House is considering “a proposal to blend legally binding conditions from an existing 1992 treaty with new voluntary pledges,” a “‘politically binding’ deal” designed to exert pressure on countries (by shame, if necessary) to reduce emissions.

While admitting that “this is the best option Obama and the rest of the world may have,” Rebecca Leber is nonetheless skeptical that it will be enough. The accord, she notes, “would likely fall short of the deep emissions cuts needed to stave off the planet’s warming by more than 3.6 degrees Fahrenheit (2 degrees Celsius) over pre-industrial levels.” And that two-degree limit, writes Bill McKibben, is “the only concrete thing that international negotiators have ever agreed on.” While he too praises the “politically ingenious” plan, McKibben is waiting for more evidence of a firm commitment to emissions reduction—noting that right now, the world is still “solidly on track for four or five degrees” of warming.

That fact should create a sense of urgency in every rational person—and maybe in members of the U.S. Congress, too. But as Ben Adler notes at Grist, no climate treaty can get a two thirds ratification in the Senate, meaning that “34 senators, representing as little as 7.5 percent of the American public if they come from the least populous states, can block any global action on climate change.” Such a tiny, unrepresentative group of senators could thereby block the United States from a formal international agreement to lower emissions, undermining our ability to bring other big emitters (especially developing countries) onboard.

Jack Goldsmith, taking a hard look at the President’s legal and political toolkit, thinks he has little to work with. First, without Senate ratification, the President’s power to forge new legally binding agreements is only derived from the terms of the existing treaty (in this case, the 1992 climate treaty). How much more he can do, pursuant to that treaty, is unclear. But moreover, the political power of Obama’s plan is limited at best:

…even if what the President signs is somehow “legally binding” under international and even domestic law, that obligation wouldn’t force Congress to “enact domestic climate change policies” or to “channel money to poor countries to help them adapt to climate change.” Nor, I think, would the President’s name on such an accord assist in shaming Congress into action. I doubt that future Congresses will be much swayed by “name and shame” pressure based on a legally controversial accord signed by a lame-duck President on a topic with strong domestic political salience.

Goldsmith’s skepticism is not unique: Even writers sympathetic to this idea seem to regard it as a long shot. But ratifying a climate treaty (or passing a meaningful climate bill) is an even longer shot. Conservatives are already denouncing this as just another Obama power grab, as though the White House’s insatiable thirst for tedious, difficult-to-negotiate international agreements, and not their own reckless intransigence, were forcing this unorthodox step. It is true that the dire threat of climate change, and the unprecedented extremism of conservatives in Congress, is forcing an unusual approach to policy-making. This is, to put it lightly, a less than ideal situation, and one that could run up against political (and more importantly, legal) limits. But to rank the delicate sensibilities of congressional Republicans over a warming planet would be a legacy that would surely haunt this President in retirement.