US officially rejoins Paris climate accord as Biden administration works on new 2030 emissions goal

World leaders welcomed the United States' official return to the Paris climate accord Friday, but politically trickier steps lie just ahead for President Joe Biden, including setting a tough national target in coming months for cutting damaging fossil fuel emissions.

And even as Biden noted the country's first day back in the climate pact, the globe's dangerous warming was just one of a long list of urgent problems he raised in a video speech to European leaders on Friday, a month into his administration. Before bringing up climate issues, he touched on the global pandemic, sputtering national economies and tense relations with China, among other matters that threaten to impede and delay tackling the nation's status as the world's top carbon polluter after China.

Despite all the other challenges, Biden said, speaking to the Munich security conference, "we can no longer delay or do the bare minimum to address climate change. This is a global existential crisis, and all of us will suffer if we fail."

Biden signed an executive order on his first day in office reversing the pullout ordered by President Donald Trump. Trump said soon after he took office that he would start the process of pulling the U.S. from the Paris accord, but it didn’t take effect until Nov. 4, 2020, because of provisions in the agreement.

RELATED: Paris Climate Agreement: What it is, how it started and what happens now that the US has rejoined

Officially, the United States was only out of the worldwide global climate pact for 107 days. It was part of Trump's withdrawal from global allegiances in general and his oft-stated but false view that global warming was a laughably mistaken take by the world's scientists.

More broadly, Trump reversed Obama-era initiatives to rein in oil, gas and coal emissions and opened new federal lands and waters to exploration and drilling. Biden is working to overturn those measures and additionally has pledged a $2 trillion remake of U.S. power grids, transportation systems and other infrastructure to sharply cut fossil fuel pollution.

While Friday’s return is heavily symbolic, world leaders say they expect America to prove its seriousness to the cause. They are particularly eager for the United States to announce its new national 2030 target for cutting fossil fuel emissions, which scientists agree are altering the Earth's climate and worsening the extremes of drought, hurricanes, flooding and other natural disasters.

United Nations Secretary-General Antonio Guterres said Thursday that the official American reentry "is itself very important," as is Biden’s announcement that the U.S. will return to providing climate aid to poorer nations, as promised in 2009.

"It’s not about how many days. It’s the political symbolism that the largest economy refuses to see the opportunity of addressing climate change." said Christiana Figueres, the former United Nations climate chief. She was one of the leading forces in hammering out the mostly voluntary 2015 agreement in which nations set their own goals to reduce greenhouse gases.

One fear was that other nations would follow America in abandoning the climate fight, but none did, Figueres said. She said the real issue was four years of climate inaction by the Trump administration. American cities, states and businesses still worked to reduce heat-trapping carbon dioxide but without the participation of the federal government.

"We’ve lost too much time," Figueres said.

RELATED: Biden signs executive orders on COVID-19, immigration, rejoining Paris climate accord and WHO

Inger Andersen, the environment program director at the United Nations, said America has to prove its leadership to the rest of the world, but she said she has no doubt it will when it submits its required emissions cutting targets.

"We hope they will translate into a very meaningful reduction of emissions, and they will be an example for other countries to follow," Guterres said.

The Biden administration is working now on a target that balances meaningful cuts in emissions with political and financial realities. Settling on a U.S. emissions goal by April, when Biden plans to host world leaders for an Earth Day summit, would help the administration prod other countries for ambitious emissions cuts as well. That spring meeting should see countries start "to put the down payments on the table," John Kerry, Biden's climate envoy, said Friday.

Republican leaders already are fighting it.

Wyoming Sen. John Barrasso, the top Republican on the Senate energy panel, has criticized Biden for rejoining the Paris accord, tweeting: "Returning to the Paris climate agreement will raise Americans’ energy costs and won’t solve climate change. The Biden administration will set unworkable targets for the United States while China and Russia can continue with business as usual."

University of Maryland environment professor Nate Hultman, who worked on the Obama administration’s official Paris goal, said he expects a 2030 target of cutting carbon dioxide emissions between 40% and 50% from the 2005 baseline levels.

A longtime international goal, included in the Paris accord with an even more stringent target, is to keep warming below 2 degrees Celsius (3.6 degrees Fahrenheit) since pre-industrial times. The world has already warmed 1.2 degrees Celsius (2.2 degrees Fahrenheit) since that time.

The United States' return to the Paris accord and an ambitious target for emissions cuts would make limiting warming "to well below 2 degrees — not just to 2 degrees but below 2 degrees — a lot more likely," said climate scientist Zeke Hausfather, energy and climate director for the Breakthrough Institute.

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Knickmeyer reported from Oklahoma City. Associated Press writer Matthew Daly in Washington contributed to this report.

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