The elephant in the room every time Americans talk about international climate agreements is that, unlike in parliamentary democracies, our opposition party gets a veto over treaties. Due to the two-thirds majority needed in the Senate for ratification of international treaties, Senate Republicans can, and will, reject any binding agreement to reduce carbon emissions (joined by some fossil fuel–state Democrats).

In theory, this means 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. The U.S. is the world’s biggest economy, and many other big nations won’t join an agreement if we won’t.

But Obama, as demonstrated by his power plant regulations, is determined to do what he can with the power he has. On Wednesday, The New York Times reported that the Obama administration is planning to go to the big climate talks in Paris next December asking for the strongest possible accord short of a treaty. “President Obama’s climate negotiators are devising what they call a ‘politically binding’ deal that would ‘name and shame’ countries into cutting their emissions,” writes the Times’ Coral Davenport. “Negotiators say it may be the only realistic path.”

Back in 1992, when Democrats were in the Senate majority and Republicans hadn’t gone off the deep end, the Senate ratified the legally nonbinding United Nations Framework Convention on Climate Change, which sets up the regular meetings to negotiate actual emissions reductions. The Obama administration would seek to expand the 1992 framework as much as possible, so that any deal reached next year would technically be an update rather than a new treaty, along with some new but mostly voluntary measures.

That might work as a way of getting around Republican opposition. But unfortunately, Republicans are not the only political obstacle to a new agreement. Throughout the wealthy Anglophone world, conservative parties are backsliding on climate change. And the conservative parties are currently in power in Australia, Canada, and the United Kingdom. Australia and Canada are particularly eager to exploit their dirty fuel resources and are doing everything they can to undermine global efforts to stave off climate apocalypse.

When Australia repealed its carbon tax last month, The Wall Street Journal noted:

In Europe, Australia’s repeal has hobbled ambitions of linking up similar carbon-emission trading systems around the globe to the EU’s own. …

In the U.S., Australia’s repeal is providing political fodder for critics of President Barack Obama ‘s climate agenda, feeding into criticism that Mr. Obama is acting alone on a problem that is stubbornly global in nature. …

Australia’s repeal also helps strengthen the position of Canadian Prime Minister Stephen Harper, who has repeatedly rejected calls from opposition politicians and environmental groups to introduce a carbon levy in Canada …

Canada formally withdrew from the Kyoto protocol on climate change in 2011, arguing the treaty would prove ineffective because it failed to incorporate major emitters such as the U.S., China and India. Mr. Harper can now point to Australia’s decision as evidence that he isn’t a global outlier, as his critics contend, when it comes to environmental policy.

Australia and Canada also undermined climate talks in Warsaw last year by refusing to contribute to a climate fund for developing nations. Australian Prime Minister Tony Abbott and Canadian Prime Minister Stephen Harper recently reasserted their skepticism of global climate agreements at a joint press conference. Climate change, said Abbott, is “not the only or even the most important problem the world faces.”

Still, conservatives in other developed countries are not as backward as their American counterparts. Domestic politics compel Abbott and Harper to admit anthropogenic climate change is happening and to at least feign a desire to address it in a way that won’t hobble their economies.

And so the Obama administration will try to thread a needle in Paris next year: get an accord that is strong enough to appease developing nations, which are calling for rich countries to reduce their emissions and contribute to the Green Climate Fund, but weak enough to appease conservatives in other developed nations.

The one thing Obama cannot do, however, is appease conservatives at home. Since they do not accept the global scientific consensus on climate change, there is no deal they will ratify. Instead, Obama must make a deal that avoids the need for Senate ratification but still has enough teeth to compel action. That’s a very fine needle to thread.

Correction: This post originally stated that meetings held under the U.N. Framework Convention on Climate Change are called protocols. In fact, they are called Conferences of the Parties (COPs).