As President Joe Biden’s conjoined infrastructure bills struggle against opposition from within his own party, much of their critical importance for addressing and mitigating climate change has been lost in the fray.

One bill, a $1 trillion injection into US roads and climate resilience efforts, was crafted with bipartisan support. But that bill’s fate is linked to a far more progressive $3.5 trillion piece of legislation that would fund – among a host of progressive social safety net measures – some of the most ambitious climate action ever taken by the United States.

For the past several weeks, however, neither bill has budged thanks to an impasse provoked by Senators Joe Manchin of West Virginia, and Krysten Sinema of Arizona – who object to the larger bill’s price tag. The party’s progressives, meanwhile, refuse to vote for the smaller bill – which omits most climate priorities – until Sinema and Manchin agree to vote for the larger legislation.

The Democrat vs Democrat squabbling has led to heated political headlines in US media as commentators puzzle over what could persuade Manchin and Sinema to get on board. But there are bigger things at stake for the world in the legislation that have been overshadowed by the feud.

In short, if the larger legislative package fails to pass, it could well mark the end of any significant US climate efforts for as long as a decade.  Because the Democrats could lose control of Congress after the 2022 midterm elections – and republicans have shown no interest in climate legislation – it could be years before another opportunity like this arises.

A failure to pass both bills would likewise leave Biden empty handed as he arrives at the COP26 United Nations climate talks in Glasgow next month, where he plans to try to convince other world leaders to take stronger climate action.

“The whole world is watching,” Rachel Kyte, dean of the Fletcher School at Tufts University and a climate adviser for the United Nations Secretary General, told the New York Times. “If these bills don’t come to pass,” she said, “then the US will be coming to Glasgow with some fine words” but “not much else. It won’t be enough.”

The climate provisions in the $3.5 trillion package are designed to rapidly transform energy and transportation, the US’s two largest sources of greenhouse gases, from systems that now mostly burn gas, oil and coal to sectors that run increasingly on clean energy from the sun, wind and nuclear power.

The impact would be broad and far reaching, from the kinds of cars that Americans drive, to the types of crops grown by farmers, to the way homes are heated and buildings are constructed. One measure could shutter virtually all of the nation’s remaining coal plants, forcing sweeping change in communities dependent on mining.  It would also, one study estimated, prevent as many as 50,000 premature deaths from pollution by 2030. And other measures would provide billions to replant in national forests and clear brush to reduce the risk of wildfire.

“Although the Biden administration put in place a number of executive orders at the beginning of his presidency, those policies will only take the United States so far,” Kelly Sims Gallagher, who worked on climate diplomacy in the Obama administration, told The Hill.  “Legislation is really essential to be able to put the United States on track for achievement of the 2025 target and of course also the new target that President Biden announced in April for 2030.”

Former President Obama committed the US to reducing its emissions 26 to 28% by 2025 compared to 2005 levels. President Biden in April said he hoped the US would cut its emissions to 50 to 52 percent of the 2005 level by 2030.

As of 2019, US emissions were down 12% from 2005 levels, and then dropped almost 10% in a single year during the covid-19 pandemic. But the International Energy Agency has warned of a spike in global emissions this year as economies reopen.

The $3.5 trillion bill – proposed by House Democrats, with no Republican backing –contains hundreds of billions in tax credits for companies that build wind and solar power or retrofit polluting facilities to capture and contain their carbon dioxide emissions before they enter the atmosphere. And it expands tax incentives for Americans to buy electric vehicles, giving consumers as much as $12,500 toward EV purchases via tax rebates. It would also penalize oil and gas companies if they leak methane, a potent greenhouse gas.

The $1 trillion infrastructure bill has bipartisan support. It would provide the largest single infusion of money to prepare communities for extreme weather fueled by climate change already underway. It includes $47 billion over five years in resilience funding to improve the nation’s flood defenses, limit damage from wildfires, develop new sources of drinking water in areas plagued by drought and relocate some communities away from high-risk areas.

But convincing self-styled moderates like Manchin and Sinema to vote for the bigger package will be difficult given the hold their corporate doners have on them. Since 2017, Manchin has been the top congressional recipient of contributions from coal-mining and oil and gas companies. Sinema is a favorite of payday lenders and airlines, both of which oppose the corporate taxes that would help fund the legislation.

Others in their party, however, say they hope they can get a deal across the finish line that would help the US restore its climate credibility on the world stage in the coming weeks.

“Glasgow is a matter of weeks away. We want the president to be able to go there with a plan to meet our emissions promises and standards,” Democratic House Speaker Nancy Pelosi, said late last month.

How hot the world ultimately gets will depend on many factors – including how other big polluting countries like China and India handle their emissions. Even so, scientists say, the chance to constrain global warming to about 1.5 degrees Celsius is growing dim.

“Even if the window for 1.5 degrees slams shut, it’s still going to be worth doing everything we can to limit as much additional warming as possible,” Michael Oppenheimer, a professor of geosciences at Princeton, told the New York Times. “Every fraction of degree of warming leads to additional damages and risks.”

Delay is not an option, Mr. Oppenheimer said. “We’ve been doing that for 40 years and now we’re finding out firsthand what that means,” he said.