NEW YORK (Bloomberg) - It took more than two decades for nations around the world to forge an agreement to save the planet from global warming. Within one year, Donald Trump could leave it in tatters.

Trump, who has said climate change is a hoax perpetrated by the Chinese, has vowed to "cancel" the Paris agreement brought into force this year by more than 190 other countries. While he can't rip up the entire accord, the real-estate tycoon and reality-television star-turned president elect has several options for pulling the US out.

A withdrawal could have significant consequences. As the richest nation on Earth and the second-largest polluter, the US's role in the Paris accord is critical, helping to secure participation from China, India and others. A withdrawal by Trump would hobble the agreement's effort to cut fossil-fuel emissions and could leave the US facing grave diplomatic repercussions.

"There would be huge implications for how other countries view the United States," said Jake Schmidt, director of the international program at the Natural Resources Defence Council, a non-profit tracking the climate talks.

"The world is united behind this agreement."

Anyone's Guess

While Trump has made it clear he plans to walk away from Paris, his precise exit strategy remains unclear.

"I don't think that's been decided," Myron Ebell, the head of Trump's Environmental Protection Agency transition team, said in an interview. "Your guess is as good as mine."

Trump has at least four options. First is to exit the Paris deal, which was signed in December. Yet, the exit clause of the agreement means the US would still be bound by it until 2020. Trump must now wait three years to formally submit his intention to withdraw and then another year before the US can exit.

There is a quicker way. Schmidt of the NRDC referred to it as "the nuclear option," which would allow the US to leave by early 2018. That would entail withdrawing from the United Nations Framework Convention on Climate Change, a treaty that established the entire process.

That deal was unanimously adopted by the US Senate and signed in 1992 by President George H.W. Bush. Trump could pull the US out with one year's notice, Dan Bodansky, an Arizona State University law professor who studies international environmental agreements, said in an interview.

While faster, that option would raise the diplomatic stakes.

"It will negatively impact his ability to get the co-operation of other world leaders on issues he cares about such as trade and terrorism," said Alden Meyer, director of strategy at the Union of Concerned Scientists, an advocacy group in Washington.

"Climate change has become a geopolitical issue of the top order."

Marrakech Talks

Trump's election comes as environment and energy ministries from around the globe gather in Marrakech, Morocco, for two weeks of talks on how to implement the Paris deal. Their meeting is organized by the United Nations and established by the 1992 framework convention that Bush signed.

The Paris deal calls for 197 countries to limit global warming to below 2 deg C and work towards net zero greenhouse gas emissions.

While Trump's victory sent shockwaves through the corridors of the conference center, Salaheddine Mezouar, a Moroccan minister of foreign affairs who is presiding over the meeting in Marrakech, said he was hopeful that the U.S. wouldn't pull out of the accord.

"The climate change question transcends politics and concerns the preservation of our livelihood, dignity and the only planet on which we all live. We are convinced that all Parties will respect their commitments and stay the course in this collective effort," Mezouar said in a statement.

Senate Option Trump could dispose of the accord by sending it to the Senate, where it would be dead on arrival in the hands of Republican lawmakers, said Myron Ebell, a director at the Washington-based Competitive Enterprise Institute. When President Barack Obama's administration negotiated the Paris deal, his envoys avoided structuring it as a traditional treaty, bypassing the need for approval from two-thirds of the U.S. Senate.

"There has been a tradition of shared power in the Constitution," said Ebell, who has also pushed for the US to stop funding UN Framework Convention on Climate Change. "President Obama has broken that precedent. So it seems to me the Senate can also break the precedent and simply take it up now."

Finally, Trump could simply ignore the US's climate goal under the Paris agreement. He could kill Obama's Clean Power Plan. And he could refuse to take any steps to reduce emissions. There is nothing in the agreement that would penalise the US for flouting its commitments.

Yet that, too, could hurt the US diplomatically. Countries are required to report their progress annually to the international community. If the US isn't making good on its promises, other nations will know.

There's also the issue of momentum and the growing global acceptance of a need to act, even among countries that still promote the burning of coal.

"The global trend to tackle global warming will not change," Koichi Yamamoto, Japan's environment minister, told reporters in Tokyo Friday.

"Not only the US, but also other countries, will not move away from that direction."

The Paris agreement has changed the tide with the view now shared that "all countries will take part and all people will be responsible for global warming," he said.