All told, the U.S. was not a participant in the Paris Agreement framework for only a few months.

On his first day in office, President Biden signed an order to rejoin the agreement. Just 30 days after Biden’s signature, the U.S. became a party to the accord once again on Friday.

But that's just a starting point for climate action. A group of states, cities and companies welcomed the milestone by launching a new coalition to push the Biden-Harris administration toward a more aggressive national commitment to cut greenhouse gas emissions.

Under the Paris Agreement, the Obama administration pledged to cut overall U.S. emissions by 26 to 28 percent from 2005 levels by 2025, but those reductions — along with commitments from other countries — are insufficient to keep temperatures below what scientists say are the most dangerous levels of warming.

The new group, called America Is All In, grew out of a coalition of subnational actors that promised to uphold the Paris Agreement under the Trump administration despite opposition at the federal level. Governors, tribal nations and environmental groups launched We Are Still In in 2017. Bloomberg Philanthropies-supported America’s Pledge was created to track progress on the group’s climate commitments.

“For four years, [the groups] acted in place of the federal government” on climate, said Jeff Nesbit, executive director of Climate Nexus, a climate communications organization. He said that We Are Still In, which Climate Nexus helped organize, “effectively held the line until this moment when a new administration entered office that took the climate crisis seriously.”

The Biden administration campaigned on an ambitious climate and clean energy platform, committing to 100 percent clean electricity nationwide by 2035 and a net-zero economy by 2050. But with a narrow Democratic majority in Congress, turning those goals into policy will be exceedingly difficult.

The new group aims to back Biden’s overarching targets with a “whole-of-society” approach. And with the support of the federal government now behind them once again, America Is All In is pushing the administration to pledge to cut emissions 50 percent below 2005 levels by 2030 on the way to net-zero carbon by midcentury.

Leaders of the new effort include: Washington Governor Jay Inslee, who ran for president in 2020 on a climate-focused platform; Mike Bloomberg, another Democratic candidate for president in 2020; Charlotte, North Carolina Mayor Vi Lyles; and Lloyd Dean, CEO of hospital chain CommonSpirit Health. The group will focus on "bottom-up" leadership in three areas: electrifying the economy, making electricity cleaner, and enacting land protection and restoration.

Climate Action Tracker, a collaboration between Climate Analytics and New Climate Institute that’s tracked global climate commitments since 2009, expects the U.S. to reduce emissions by 20 to 21 percent below 2005 levels by 2020, with cuts due in large part to a precipitous drop in emissions that was tied to the pandemic. That analysis forecasts the U.S. could reach the lower bound of its Paris Agreement target.

But as part of the Paris Agreement, global governments are expected to increase the ambition of their commitments over time. Most countries have not yet submitted the new targets that were due by the end of 2020, according to the World Resources Institute. The U.S. is expected to release its new target this spring.

The group of subnational actors represented by We Are Still In and America’s Pledge account for more than 50 percent of U.S. greenhouse gas emissions. An analysis from America’s Pledge suggested those actors could reduce greenhouse gas emissions 37 percent below 2005 levels by 2030. But the group said deeper cuts will require leadership from the federal government.  

A December report from Environmental Defense Fund underscores the difficulty states face in meeting climate targets. The environmental group’s analysis showed that the 25 states plus Puerto Rico that committed individually to upholding the Paris Agreement will fall short.

The new group emphasizes the need to integrate its bottom-up approach with federal leadership.

“Over the last few years, America's Pledge has repeatedly demonstrated the immense power, potential and significance of non-federal [climate] leadership, not just domestically but [also] on the world stage,” said Wendy Jaglom, manager of the U.S. program at Rocky Mountain Institute, another organization that works on the initiative. “It’s this combination of the two — non-federal leadership combined with the federal government — that can get us back on track for U.S. climate action.”