Mr. Trump has offered to “renegotiate” the Paris deal, because he says other countries are “laughing at us” while they renege on their pledges. While countries like France and Germany have ruled out a broad renegotiation of the agreement, the United States could nonetheless try to shape the rules from within.
“The question is whether the Trump administration still shows up for those discussions,” said Andrew Light, a senior climate change adviser at the State Department under President Barack Obama. “If they really are pushing to ‘renegotiate’ the deal, as they say, I don’t see why they wouldn’t go.”
Another thing to watch this fall: a growing coalition of states, cities and companies that are pledging to do as much as they can to meet the United States’ climate goals on their own. They will probably send a delegation to Bonn to reassure other countries that the United States is not completely out of the game.
Everyone agrees that current pledges under the Paris agreement are nowhere near sufficient to keep total global warming well below 2 degrees Celsius, the threshold widely deemed unacceptably risky.
So, starting in 2018, countries have agreed to meet every five years to take stock of their emissions-cutting efforts to date, compare them with what is needed to stay below 2 degrees of warming, and then figure out how to ratchet up their ambitions. As part of this effort, countries will urge one another to make their existing pledges on emissions stronger. The Paris deal was meant to work through peer pressure, and experts say this “global stocktake” exercise is crucial for that.
The United States is also free to join these discussions, but it seems unlikely that the Trump administration will submit a stronger pledge. Some experts also fear that the United States could play a spoiler role in these discussions, in much the way that major oil producers like Saudi Arabia or Russia have done in the past.
Nov. 4, 2019
This is the earliest date that the United States can submit a written notice to the United Nations that it is withdrawing from the Paris deal — exactly three years after it came into force. As soon as that happens, the United States can leave the accord in exactly one year. (The Trump administration could also change its mind at any point beforehand and decide to stay in.)
Nov. 4, 2020
This is the earliest that the United States could officially withdraw from the climate accord. By coincidence, it would happen one day after the next presidential election.
Also by 2020, other countries are scheduled to offer new or updated commitments for how they plan to tackle climate change under the Paris deal. One question is whether the American exit might make these plans weaker than they otherwise would be. “My biggest worry is the corrosive effect on global ambitions,” said Elliot Diringer, executive vice president of the Center for Climate and Energy Solutions.
The Obama administration originally pledged that the United States’ greenhouse gas emissions would fall roughly 17 percent below 2005 levels by 2020. Emissions are currently about 12 percent below 2005 levels, and it remains uncertain how much further they will fall. The Trump administration is scrapping federal climate policies like the Clean Power Plan, but many states are pushing to expand renewable energy and shift away from coal power. If the United States comes close to its 2020 target, experts say, that may help persuade other countries in Paris not to scale back their own efforts.
If a new president enters the White House on Jan. 20, 2021, he or she could easily submit a written notice to the United Nations that the United States would like to rejoin the Paris accord. Within 30 days, the United States could re-enter the agreement and submit a new pledge for how the country plans to tackle climate change.
If the United States does rejoin Paris, however, it could take time to regain the credibility it once had within climate discussions. “Other countries are certainly going to wonder if the American political system is just too volatile to be relied on for consistency on this issue,” Mr. Light said.
Negotiators will meet again in 2023 to see how their second round of pledges and actions stack up against the 2-degree goal. The idea is that they will continually increase their ambitions and meet every five years to adjust accordingly.
The Obama administration vowed to cut greenhouse gas emissions 26 to 28 percent below 2005 levels by 2025 as part of the Paris deal. Even before Mr. Trump came into office, that target would have been difficult to reach without new policies, and it may prove unattainable now.
Other countries will be watching how close the United States may come. A recent analysis by the Rhodium Group estimated that United States emissions will now most likely fall 15 to 19 percent below 2005 levels by 2025, when taking into account both the effects of Mr. Trump’s policies and initiatives that states are pursuing.
But emissions could fall further if technologies like electric cars or solar power proliferate faster than expected, or if Congress or a new administration enacts additional policies, like a price on carbon. All of those factors could influence what actions other countries decide to take on climate change.