MARRAKECH, Morocco—Less than a year ago, representatives from nearly 200 countries celebrated in the French capital on the adoption of the Paris Agreement, the first-ever global climate pact. An exhausted French Foreign Minister Laurent Fabius, who presided over the Paris talks, capped two weeks of high-pressure negotiations by declaring the deal a “historical turning point” as he wiped tears from his eyes.

In the space of a few remarkable hours last week—as the United States presidential election results trickled in during the early hours of Wednesday morning—all that may have changed, shrouding in doubt that same celebrated Paris deal that aims to reduce greenhouse gas emissions and avoid the worst impacts of climate change.

The latest round of United Nations climate talks, the follow-up to last year’s summit, is taking place in Marrakech, Morocco. The negotiations got under way a week ago with the goal of starting a three-year process to complete a “rulebook” that will implement the Paris deal, which entered into force just days before the opening gavel in Marrakech. With Donald Trump’s victory over Hillary Clinton, focus at the talks shifted away from that process to how international efforts to confront climate change could weather a potential withdrawal by the United States, the world’s largest economy and second-largest emitter of greenhouse gases.

Progress at the talks slowed to a crawl on Election Day in nervous anticipation of the results. Many stayed up all night to monitor the results. Trump’s unexpected victory stunned those in attendance. One veteran observer said Wednesday morning that “everyone is either asleep at their desks or in a state of shock.” The election results have been the main topic of discussion at Bab Ighli, the tent city Morocco constructed to host the talks.

“For people who have been around this process for a long time, there is a feeling of ‘Uh-oh, here we go again,’ ” said Alden Meyer, director of strategy and policy for the U.S.-based Union of Concerned Scientists, who is attending the Marrakech talks.

Before the Paris Agreement, there was the 1997 Kyoto Protocol, which required action from only three dozen wealthy, industrialized countries. The Kyoto treaty never had the wide-ranging impact its architects intended because it was crippled by President George W. Bush’s decision to withdraw the U.S. from the deal.

The U.S. position shifted under President Barack Obama, and the country played an important leadership role in the run-up to the Paris Agreement. A high-profile deal in 2015 between the U.S. and China, the world’s two largest polluters, to curb their greenhouse gas emissions gave needed momentum to the negotiation process three months before delegates gathered in Paris.

Now there are fears the U.S. position may swing back the other way. During the electoral campaign, Trump called climate change a “hoax,” and he promised to “cancel” the Paris deal if elected. Since Trump’s victory, the only hint of his plans regarding climate change was appointing Myron Ebell, a notorious climate skeptic, to head the transition process at the U.S. Environmental Protection Agency. But on Monday, Reuters cited an unnamed source close to the incoming administration as saying that Trump wanted to quickly withdraw from the Paris Agreement. The Marrakech talks are rife with speculation about how Trump might choose to pull out of the Paris deal when he takes office in January. If he does, that will make the Paris Agreement far less effective in terms of reducing emissions and will also hurt efforts to provide financial aid to poor countries to adapt to climate change and transition to renewable energy. (The Obama administration pledged to provide $3 billion over five years for such initiatives.)

One option for the incoming administration is a formal withdrawal, a complicated process that would require four years to complete.

Another possibility is for the U.S. to disregard its voluntary Paris Agreement target to reduce emissions between 26 and 28 percent by 2025, compared with 2005 levels, by dismantling the Obama administration’s Clean Power Plan. (Ebell refers to it as the “Costly Energy Plan.”) The downside: It is possible the rulebook being drafted in Marrakech could be written to include sanctions for countries that fail to meet their Paris Agreement pledges, though legal experts say it is not clear how biting sanctions could be or how they would be imposed.

According to several media outlets quoting sources close to Trump, the most likely possibility is a complete withdrawal from the 1992 U.N. Framework Convention on Climate Change, which would erase Paris Agreement obligations but also rob the U.S. of a seat at the table for future negotiations. That move would only require a one-year wait, meaning the U.S. could be free of international climate obligations as soon as January 2018. A big risk, however, is that without U.S. involvement, the rulebook could be written to punish the U.S. or other countries not participating in the Paris Agreement with an emissions-based tariff or a levy on energy imports.

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In public at least, few are talking about that prospect at this point. Instead, officials said they’re taking a wait-and-see attitude and hoping for the best when it comes to Trump’s plans.

Chen Zhihua, a Chinese delegate, brushed aside concerns that the U.S.-China bilateral agreement might need to be renegotiated.

“We recognize there may be a difference between campaign rhetoric and the way a leader governs,” Chen said at a crowded Friday briefing. “We will wait to discuss with President Trump when he takes office. Until then, nothing has changed.”

Ségolène Royal, France’s minister of ecology, sustainable development, and energy, told reporters Friday that she was hopeful a new Trump administration would recognize the value of continued engagement in the climate negotiation process.

“The transformation to a green economy creates good jobs and sparks economic growth while also helping the climate,” Royal said.

In more than a dozen briefings since the election results became final, almost everyone—whether delegates, U.N. officials, or environmentalists—insisted the process will move forward no matter what the new president does.

“The Paris Agreement speaks volumes about the global determination and international cooperation to do what is best for humanity,” said Elina Bardram, the European Union’s chief negotiator in Marrakech. “That cannot be undone by any one country.”

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Hugh Sealy, a negotiator representing small island nations, was defiant: “No matter what happens, it will not stop us from acting,” he said. “We will just have to redouble our efforts.”

But in private, frustrated participants in Marrakech took a different tone. Delegates, U.N. officials, and other observers almost always agreed to speak candidly only on the condition of anonymity. But their views were mostly consistent.

“We’ve got a delicate mechanism constructed over the course of several years, and now one of the countries playing a leadership role in the process has elected a president who does not think climate change is a problem,” one high-ranking European negotiator said. “It’s easy for us to worry.”

A veteran United Nations official agreed: “Put it this way,” he said. “This process has just been dealt a very bad hand of cards.”

Youth observers in Marrakech, however, had no problem expressing their disappointment openly. The days since the election saw several youth-led demonstrations in the main facility in Marrakech, with delegates and other participants scurrying by en route to meetings or plenaries.

A youth-driven social media hashtag, #EarthToMarrakech, began trending in the wake of the elections. It featured news of protests, calls for leaders to take action despite the developments in the U.S.

“Trump is an embarrassment in many ways, and we have all read that he has many problematic policies,” said Marc Gunter, a 22-year-old youth delegate from Hamburg, Germany, who wore a shirt adorned with a drowning polar bear. “But climate change is different from some domestic policy. If he tears up the Paris Agreement, it will have an impact on everyone in the world.”

Herve Santoro, 21, a youth delegate from Toulouse, France, echoed those remarks. “Of course we are worried,” Santoro said, holding a sign reading “Accelerating Climate Action.” “We are the ones who have to live in the world Trump and his generation will leave behind.”