On Earth Day, April 22nd, President Barack Obama plans to sign the Paris Climate Agreement along with representatives from about 130 other countries. According to the text of the Agreement, it "shall enter into force on the thirtieth day after the date on which at least 55 Parties to the Convention accounting in total for at least an estimated 55 percent of the total global greenhouse gas emissions have deposited their instruments of ratification, acceptance, approval or accession." It is the position of the Obama Administration that the Paris Agreement is not a formal treaty requiring Senatorial advice and consent, so issuing an executive agreement is supposed to be enough to commit the U.S. to abiding by its provisions. Since 130 countries are going to sign on April 22, the 30-day clock for coming into force could begin ticking and the Agreement could come into force as early as June. In other words, the U.S. could well be committed to honoring the Agreement before the election of the next president, be the winner Trump, Cruz, Sanders, Clinton, or Johnson.
Once the Agreement is in force, according to Article 28: "At any time after three years from the date on which this Agreement has entered into force for a Party, that Party may withdraw from this Agreement by giving written notification to the Depositary." Furthermore, the official withdrawal can take place only after waiting an additional year. That means that U.S. commitments could last through 2020.
The Washington Post notes:
Any attempt to abandon or withdraw from the Paris agreement — either before or after its entry into force — would likely create international uproar.
"Entry into force does in a sense create a higher hurdle in terms of reversing course essentially. But the political consequences are there under any circumstances," says David Waskow, who directs the international climate initiative at the World Resources Institute.
In March, Trump told the Washington Post, "I think there's a change in weather. I am not a great believer in man-made climate change. I'm not a great believer."
For a would-be president who aims to force Mexico to build a border wall, the consequences of ignoring the Paris Climate Agreement would be pretty small potatoes. Consider what happened to countries—Canada and Japan—that violated their solemn treay obligations to cut greenhouse gases under the "legally-binding" Kyoto Protocol. Nothing.
That being said, see for more background my December 9 Paris dispatch, "Bottom-Up Paris Climate Accord May Surprise Activists and Skeptics."