UNITED NATIONS — More than 20 world leaders tendered legal documents on Wednesday, formally binding their governments to the Paris climate accord at a General Assembly ceremony here and all but ensuring that the agreement will go into force by the end of the year.
The specifics of each country’s plans, though, are voluntary. There are no sanctions for failing to control pollution or to put economic polices into practice, or for submitting unambitious pledges.
The legally binding portion of the Paris accord does little more than require governments to continue to convene at high-profile global climate summit meetings, make public pledges to tackle global warming at home and submit those plans to be published on a United Nations website.
The ultimate importance of the climate accord will be determined by its members.
“If enough countries start implementing the Paris agreement, historians will see this as a watershed moment,” said Erik Solheim, director of the United Nations environment program. “But if we don’t implement it, this will just be bringing a bunch of politicians together around a piece of paper.”
In total, 60 countries representing 48 percent of global planet-warming emissions have now legally bound themselves to the Paris accord. The deal goes into legal force when at least 55 countries representing 55 percent of global emissions sign on. At Wednesday’s ceremony, leaders of countries representing at least an additional 12 percent of global emissions pledged to submit their legal documents by the end of this year. If they follow through, the pact will take effect.
“What once seemed impossible now appears inevitable,” said Ban Ki-moon, the United Nations secretary general, who will step down from his position at the end of the year.
Some of the plans that were already submitted, such as those of the United States, the world’s second-largest greenhouse polluter, have hard targets backed up with detailed policy pledges. The Obama administration promised that by 2025, aggressive regulations designed to shut down coal-fired power plants will cut the nation’s emissions by 26 percent to 28 percent from 2005 levels.
Even that plan stands in legal limbo. Twenty-seven states have sued the administration to stop it, and the Supreme Court has halted it until the suit is resolved.
Other plans are less aggressive and less detailed. India, the world’s third-largest polluter, would essentially allow its emissions to triple by 2030 — an improvement, Indian officials say, from the sevenfold increase in emissions without any action. Exactly how India can carry out that plan, which includes a significant increase in solar power, is not clear. India’s climate strategy does include references to Gandhi and yoga.
“Obviously, ratifying Paris quickly is better than doing it slowly,” said Christoffer Ringnes Klyve, director of climate and environment programs at Future in Our Hands, a Norwegian advocacy group. “But there are lots of problems with the Paris agreement, and lots of problems with the countries that are ratifying it not having the faintest idea how they’re going to achieve the goals
Countries will be legally bound to attend summit meetings where they must give progress reports on their commitments. After 2025, countries must draw up more stringent emissions reduction plans, although the Paris pact does not say how much more stringent those plans should be.
“If I’m Singapore and I see China’s doing it, that leads me to do it,” said Jonathan Pershing, the American climate envoy. “If I’m a Latin American country and I see Mexico’s doing it, I’ll do it too.”
But that strategy does not account for leaders who do not care about global opinion. Donald J. Trump, the Republican nominee for president, has called climate change a hoax and vowed to withdraw the United States from the Paris agreement if he is elected. Once the deal has entered into force, all countries will be legally bound to it for four years. But a Trump administration could refuse to attend summit meetings or submit plans or progress reports, with no consequences beyond lacerating speeches at United Nations podiums.
That attitude appears to be shared by President Vladimir V. Putin of Russia, the world’s fourth-largest climate polluter. Russia put forth a plan that is essentially business as usual, requiring no new domestic policies.
At the next major United Nations climate change summit meeting in November in Marrakesh, Morocco, diplomats hope to create an independent body to monitor and verify countries’ pollution levels — and to use public scrutiny to push countries to reduce their emissions. If each nation’s pollution levels are publicly reported on a website that showcases apples-to-apples comparisons of progress, governments will be more inclined to act, diplomats reason.
But several countries, including China and India, are expected to push for a more lenient system that is reliant on self-reporting.
“There is an expectation that people will report their emissions. But how does that happen?” said Jo Tyndall, the climate change envoy of New Zealand, who played a central role in brokering the Paris agreement. “What’s the process for review? Who will review?”
In Marrakesh, countries will also take up the thorny question of money: Under the Paris deal, rich countries voluntarily pledged to spend $100 billion annually by 2020 to help poor countries adapt to climate change and develop new clean energy technologies. There is already resistance in several countries, particularly the United States. Peer pressure may be enough to persuade countries to sign on to a global deal, but diplomats fear it may not be enough to open their wallets.