It's official. The United States is fully part of the Paris Climate Agreement.

On April 21, the administration submitted its plan to the United Nations to reduce greenhouse gas emissions by at least 50% from where they were in 2005 by the year 2030.

"We'll get there by investing in American workers, American jobs, American infrastructure, and building a stronger and more resilient economy," President Joe Biden said April 23.

That puts a positive light on the work that lies ahead. While several independent studies say Biden's targets are achievable, a host of challenges await.

Work by the University of Maryland's Center for Global Sustainability found that in two key areas — electricity generation and transportation — major reductions are possible. But the report highlighted that gains must be made across every part of the economy.

"Only through a combination of actions across all sectors of the economy will it be possible to achieve highly ambitious reductions approaching 50% or more," the March 2021 study said.

An analysis from the Asia Society Policy Institute said that between federal and state level actions, reductions could reach 54% from 2005 levels. The caveat was that perhaps only half that goal could be reached if Congress didn't support Biden's plans.

The spending required to develop renewable power, make buildings more efficient, ease the shift of workers into low-carbon producing jobs, and a host of other changes hinges on congressional approval — as do many regulatory changes that would span many industries.

Biden's infrastructure proposal could help progress toward those goals, but it faces an uncertain future.

"The big question is whether he will be able to overcome stiff political challenges," wrote Samantha Gross, the director of the Brookings Institution's energy security and climate initiative. "Congressional Republicans might be able to find something to like in supporting popular technologies, like clean energy or electric vehicles, but so far, that's not happening."

Nevertheless, Biden said he would rejoin the Paris Agreement, and he has.

We rate this a Promise Kept.

On his first day in office, President Joe Biden signed an executive action that brought the United States back into the Paris Climate Agreement. Here's the full text:

"I, Joseph R. Biden Jr., President of the United States of America, having seen and considered the Paris Agreement, done at Paris on December 12, 2015, do hereby accept the said Agreement and every article and clause thereof on behalf of the United States of America."

The change takes place in short order. The administration sends a letter to the United Nations requesting membership, and formal re-entry will come about a month from now. 

Biden enjoys a relatively free hand here.

President Barack Obama brought the U.S. into the agreement through an executive action in 2016. No Senate signoff was involved. President Donald Trump pulled the country out the same way.

But while Biden can flip the switch with his own executive action, he will then need to set the country's greenhouse gas reduction target under the deal.

"The one we had before is way out of date," said Timothy Profeta, director of the Nicholas Institute for Environmental Policy Solutions at Duke University. "He'll have to assess what he can achieve. It has to be in keeping with his ambitions, but it also has to rebuild America's credibility with the international community."

The Paris accord has several ambitious goals. Signatories agreed to do their part to reduce greenhouse gas emissions and keep the world's temperature to just 1.5 degrees Celsius above what it was before industrial production took root.  

Each country set its own targets, with reductions to begin in 2020. By midcentury, the goal would be zero greenhouse gas emissions.

The Obama administration had set its target at 26% to 28% below 2005 emissions levels by 2025. Biden has set a broader goal of net-zero greenhouse gas emissions by 2050.

Trump pulled the country out of the agreement in 2017. We found that many of his criticisms of the program were inaccurate to varying degrees. Despite Trump's early action, under the terms of the agreement, U.S. participation didn't formally lapse until Nov. 4, 2020.

We'll update this when the U.N. approves America's re-entry. For now, it is In the Works.