With the United States rejoining the Paris Agreement, the country must look beyond faster, deeper carbon cuts at home and step up with a fair share financing commitment to help developing countries do the same, Eco Equity Executive Director Tom Athanasiou argues in a new post for The Nation.

“Despite its many and substantial flaws, the Paris Agreement put in place a foundation that participating nations could, in principle, use to build institutions and processes that deliver a rapid international climate transition,” Athanasiou writes. “It was never intended to be the end of the story. In fact, its so-called ‘ambition mechanism’ by which national pledges are repeatedly strengthened is still missing its crucial finance and assessment provisions.”

And yet, while time is running short for the “Herculean” effort that will be needed to hold average global warming at 2.0°C, much less 1.5°C, “the basic architecture of an international transition strategy is in place. Its core is an open-ended series of five-year cycles in which the pledges are intended to become ever stronger. The first cycle began in Paris. The second, which the pandemic delayed, is now beginning and brings with it the good news that the national pledges are being strengthened—and could be strengthened further by a considerable margin.”

But countries’ recent commitments to “build back better” are just one part of the solution, he says. Even though 130 countries representing 51% of global emissions have promised to hit a net-zero target by mid-century—the U.S. would bring that to 63%—the success of the Paris accord will still come down to climate finance.

“No matter how transformative the renewables revolution turns out to be, to rapidly transform the global economy from its current overwhelming reliance on fossil fuels will require lots of financial help,” Athanasiou writes. “The European Union has announced it will reduce its emissions by 55% by 2030, and China pledges ‘carbon neutrality’ by 2060. But the world’s less wealthy countries cannot be expected to follow rapidly without significant infusions of financial and technological support. Poverty alleviation and development are the proper objectives of poorer countries, and they will not act with sufficient resolve to decarbonize their economies unless they can do so while pursuing those goals.”

So far, the EU has promised to double its contribution to the UN Green Climate Fund, while outgoing president Barack Obama pledged $3 billion, only to have Donald Trump claw back $2 billion of that commitment.

“It was a travesty, but hardly a unique one,” Athanasiou writes. “In Copenhagen, in 2009, the rich nations pledged $100 billion per year to help developing countries make the climate transition but, according to Oxfam International, the support they’ve actually delivered amounts to $19 billion to $22 billion per year. Biden has said he wants the United States to return to Paris as a ‘climate leader’. He’ll have to start by paying Trump’s $2-billion debt, and then matching the European move by doubling the United States’ initial pledge. That’ll be $8 billion, to get back in the game.”

Which in the scheme of things is a small fraction of the $2 trillion Biden has promised to invest in climate action, the $2.7 trillion the 25 largest global banks have invested in fossil fuel projects since the 2015 Paris conference, the $242 billion in COVID relief money the G20 had directed to “high-carbon activities and fossil energy” as of February 10, or the $70 billion in fossil spending from Trump.

“To salvage the climate future will require a new internationalism—and a shared mobilization in which the United States does its fair share, especially by helping developing countries limit their own emissions,” Athanasiou says. “Bernie Sanders’s Green New Deal proposal, which addressed this need, asserted that a U.S. fair share would be 161%, including a 71% drop in domestic emissions. Sanders further proposed that the United States provide $200 billion to the Green Climate Fund for the period from 2020 to 2030—about $20 billion a year.”

That funding “would absolutely be a game-changer that would demonstrate real American leadership in the global climate struggle.”