“Syria’s participation puts an exclamation point on the fact that the U.S. actions are contrary to the political actions, and the sincerely held beliefs, of every other country on the face of the Earth,” said Michael Oppenheimer, a professor of geosciences at Princeton University and a longtime observer of UN climate negotiations.

The United States is “the only powerful country” that has disavowed the treaty, he said. “And that was the case from the day it withdrew.”

“I find it ironic that the government of Syria would say that it wants to be involved [in the Paris Agreement] and that it cares so much in climate and things like CO2 gases,” said Heather Nauert, a spokesperson for the State Department, at a briefing on Tuesday. “If the government of Syria cared so much about what was put in the air, then it wouldn’t be gassing its own people.”

The People’s Council of Syria may not have made the decision to enter the Paris Agreement in the first place. Syria has been engaged in a horrific civil war since 2011, and the areas under government control are tightly ruled by President Bashar al-Assad. The United Nations has implicated Assad in war crimes, including sarin-gas attacks on Syrian children. Assad’s family has run the country since 1971.

Syria has not yet submitted a plan to reduce its greenhouse-gas emissions, as the Paris Agreement requires. In fact, preparing a plan to emit less carbon pollution is just about the only thing the Paris treaty requires.

“I don’t know what the reasons are that Syria chose to focus on this now. It’s got enough problems and doesn’t want to be seen as an outlier in any other way,” Oppenheimer told me.

Its acceptance of the accord can also be seen as a kind of geopolitical troll. Since Nicaragua signed onto Paris last month, Syria was the only remaining country left out of the Paris process. Nicaragua gets almost all of its energy from renewable sources, and it declined to join the treaty in 2015 because it said the accord did not go far enough.

Some analysts have argued that Syria’s decision to join the Paris treaty shows that the agreement is a weak or toothless document. The Paris Agreement, after all, sets few limits on its signatories. Most importantly, it allows countries to set their own emission-reduction goals, rather than imposing them as part of the treaty text.

The United States has never taken issue with the treaty’s toothlessness. In fact, the Paris accord adopts a “bottom-up” strategy in part because the United States has long insisted on it. In 2007, President George W. Bush’s administration began arguing for a “pledge-and-review” climate treaty, similar to the one adopted in Paris. Half a decade later, the Obama White House and the United Nations used a broader version of that plan as they began work on what became the Paris Agreement.