Paris climate agreement summary: What is it, how would Trump withdraw and how will the world react?

President Donald Trump is said to be considering withdrawing the United States from the Paris climate agreement, a landmark accord reached in 2015 between 195 countries that seeks to avoid some of the worst effects of climate change by curbing global greenhouse gas emissions.

The White House says it has not yet reached a final decision on Paris, and hundreds of corporations and world leaders are lobbying the United States to stay in the pact. Within the administration, some senior officials, including Secretary of State Rex Tillerson, have warned the president that the diplomatic repercussions from leaving could be severe.

A US withdrawal would not scuttle the Paris accord, but it could seriously weaken global efforts to avoid drastic climate change. Here’s a primer on how the Paris agreement works — and what could happen if the United States leaves.

A: Under the Paris agreement, every country submitted an individual plan to tackle its greenhouse gas emissions and then agreed to meet regularly to review their progress and prod one another to ratchet up their efforts as the years went by.

Unlike its predecessor treaty, the Kyoto Protocol, the Paris deal was intended to be nonbinding, so that countries could tailor their climate plans to their domestic situations and alter them as circumstances changed. There are no penalties for falling short of declared targets. The hope was that, through peer pressure and diplomacy, these policies would be strengthened over time.

Under the deal, the Obama administration pledged to cut domestic greenhouse gas emissions 26 to 28 percent below 2005 levels by 2025 as well as to commit up to $3 billion in aid for poorer countries by 2020. (The United States has delivered $1 billion to date.) China vowed that its emissions would peak around 2030 and that it would get about 20 percent of its electricity from carbon-free sources by then. India would continue to reduce its carbon intensity, or CO2 output per unit of economic activity, in line with historical levels.

While the current pledges would not prevent global temperatures from rising more than two degrees Celsius above preindustrial levels, the threshold deemed unacceptably risky, there is some evidence that the Paris deal’s “soft diplomacy” is nudging countries toward greater action. A recent study from the Grantham Research Institute found that the mere existence of the accord had prodded dozens of countries to enact new clean-energy laws.

A: Because the deal is nonbinding, there are no penalties if the United States pulls out.

The Trump administration can invoke the accord’s formal withdrawal mechanism, which takes four years — though US officials could stop participating in any future climate talks immediately. A future administration could, if it chose, rejoin.

More radically, the Trump administration could withdraw from the underlying United Nations Framework Convention on Climate Change, signalling a withdrawal from all UN-sponsored climate discussions. It is not yet clear which option the Trump administration would choose, if it decides to leave.

If the United States does leave, it would join Syria and Nicaragua as the only two countries not participating in the accord.

The United States could also face serious diplomatic repercussions for leaving. Europe, China and other countries may threaten to withhold cooperation on issues the Trump administration cares about. In a more extreme case, other countries could decide to impose carbon tariffs on the United States.

A: Whether or not the United States leaves Paris, the Trump administration will keep trying to dismantle the Obama administration’s domestic climate policies, including the Clean Power Plan to curtail emissions from power plants, and various regulations on methane leaks from oil and gas operations. Those rollbacks are still far from assured, however, and environmentalists plan to challenge them in court.

Pulling out of Paris will not mean the end of all domestic efforts to reduce emissions. States like California and New York plan to keep pursuing their own programmes to clean up power plants and vehicles. And the private sector is already shifting toward cleaner energy: Cheap natural gas and renewables will continue to drive the retirement of coal plants.

But the United States will be doing far less about global warming than it otherwise might have done. A recent analysis by the Rhodium Group estimated that, under Trump’s policies, US emissions will now most likely fall 15 to 19 percent below 2005 levels by 2025, rather than the 26 to 28 percent that the Obama administration pledged.

A: Withdrawal by the United States could seriously undermine global efforts to tackle global warming — but much will depend on how other countries react.

Leaders in Europe, China and India have insisted that they will carry on tackling global warming without the United States. But the precise shape of future climate talks remains an open question.

One possibility is that, with the world’s second-largest emitter pulling out, other countries may feel inclined to relax their own plans to curb greenhouse gases. “Even in places like Europe, you have industry groups worried about competitiveness,” said David G. Victor, a professor of international relations at the University of California, San Diego. A US withdrawal, he notes, “makes the politics in other countries that much harder.”

Developing countries like India, Indonesia, and the Philippines may be more reluctant to tackle their emissions if the United States pulls back on promised aid to help them adjust to the worst effects of climate change.

Not everyone is so pessimistic, however. Luke Kemp, a climate policy expert at Australian National University, suggests that other countries may choose to redouble their pursuit of cleaner energy in the face of recalcitrance from the Trump administration. “In the short term you could see a galvanising effect,” he said.

China, the world’s largest emitter, is poised to assume a dominant role in future talks. The country is investing heavily in wind, solar and nuclear power in an attempt to level off its once-insatiable coal consumption. But it is unclear how far China’s leaders will go in pressuring other countries to raise their ambitions. In the past, China has argued against rigorous transparency standards to review nations’ progress.

But the rest of the world will have a lot of heavy lifting ahead of it: Current pledges, when added up, put the planet on pace to warm three degrees Celsius or more above preindustrial levels, an outcome with a far greater risk of destabilising ice sheets in Greenland and Antarctica, higher levels of sea-level rise, more destructive heat waves and droughts, and the loss of vital ecosystems like coral reefs.

One final variable: A future US administration could always change course on climate policy — and even try to rejoin the agreement once Trump is out of office.

“Other countries are constantly judging each other’s positions in the world,” Victor said. “If it looks like this administration is only going to last for four years, you might see other countries continue to push along on climate and not give up on the US just yet.”

Copyright The New York Times