Senate Majority Leader Chuck Schumer speaks to House Speaker Nancy Pelosi outside the Capitol in June.
CNN  — 

After decades of inaction from the United States on climate, President Joe Biden and congressional Democrats face a reckoning.

Biden has big climate ambitions, vowing in April to cut greenhouse gas emissions in half by 2030. The world is watching closely to see whether the US will deliver on that promise, as the President’s climate envoy, John Kerry, prepares to meet with global leaders in November for the United Nations climate summit.

Jonathan Pershing, one of Kerry’s senior advisers, recently told lawmakers the US needs to “walk the talk” to regain its climate credibility on the world stage. What’s not clear is whether the President has the votes in Congress — even within his own party — to get it done.

As the drought and extreme weather intensify, Democrats view the massive budget bill and its significant climate provisions as their last, best hope to achieve something meaningful on climate as the crisis worsens. In August, global scientists reported the planet is quickly approaching the critical warming threshold of 1.5 degrees Celsius above pre-industrial levels, below which they say the planet must stay in order to avoid the worst consequences.

Within the US, pressure is mounting after a series of climate disasters this summer, including record-breaking wildfires, deadly heat, water shortages and a disastrous hurricane that’s expected to cost the US economy billions.

“Scientists have been warning us for years that extreme weather is gonna get more extreme. We’re living it in real time now,” Biden said Monday as he toured wildfire damage in California.

Touting the budget and infrastructure bills, the President urged people to “think big.”

“Thinking small is a prescription for disaster,” Biden said. “We’re gonna get this done, this nation’s gonna come together and we are going to beat this climate change.”

Congressional leaders have set an end-of-September deadline in the House to pass their massive budget bill alongside a separate bipartisan infrastructure bill. Together, the packages contain hundreds of billions of new climate investments, which Senate Majority Leader Chuck Schumer argued will get the US most of the way to hitting Biden’s fossil-fuel emissions target of 50-52% below 2005 levels by 2030.

With a razor-thin majority in both the House and Senate, this is Democrats’ only shot at passing a substantial climate bill before world leaders meet in November. But there’s at least one prominent Senate Democrat who could thwart those plans.

Sen. Joe Manchin, second left, during a bipartisan press conference to promote the infrastructure bill in July.

Sen. Joe Manchin of West Virginia, Senate Democrats’ key swing vote, wants to pare down the overall size of the bill, and he has said he has concerns about what the climate provisions could mean for a fossil-fuel producing state like West Virginia. As chair of the Senate Energy and Natural Resources Committee, the senator will have a large hand in shaping Democrats clean electricity program.

Sen. Sheldon Whitehouse of Rhode Island told CNN negotiations with Manchin are ongoing — but he was optimistic the West Virginia senator would understand the gravity of a fast-warming climate and its impacts.

“At the end of the day, we’re all answerable to the future to get the job done right,” Whitehouse said. “I don’t think [Manchin] wants to be on the wrong side of that future.”

How the bill would tackle the climate crisis

After years of inaction in the White House and Congress, Biden’s budget bill represents decades worth of policy in a single bill. Experts told CNN it represents a paradigm shift in how to tackle climate change — moving the entire economy away from fossil fuels and toward clean energy.

“Moving the US economy is equivalent of changing the direction of an enormous ocean liner,” Josh Freed, founder of the Climate and Energy Program at the center-left think tank Third Way, told CNN. “It takes time to do but once you have it going in the right direction it can pick up steam and get going quickly.”

After re-entering the US into the Paris Climate Accord in January, Biden announced a target to reduce greenhouse gas emissions by 50% to 52% relative to 2005 levels by 2030.

That target could be met in part through federal regulations restricting emissions from vehicles and power plants. A White House spokesperson told CNN the Biden administration sees its climate actions coming both from Congress and executive action.

“We also believe that there exists a number of paths to meeting our emission goals and targets,” the spokesperson said. “The Biden climate agenda doesn’t hinge on reconciliation or the infrastructure package alone. Rather, it is integrated throughout both — and it is a key part of everything we do in the whole of government effort launched on day one.”

But experts told CNN that Biden needs Congress to pass massive investments in renewable energy, electric vehicles and other green programs to truly make a dent in US carbon emissions.

President Biden meets with smoke jumpers and other firefighting professionals during a tour at the National Interagency Fire Center on Monday.

A clean electricity program is Democrats’ cornerstone climate initiative in the massive budget bill. It would promote a transition away from fossil fuels by paying electric utilities who increase the amount of renewables and other forms of clean power and penalizing those who don’t meet clean targets.

Generating electricity from non-fossil fuel sources like wind, solar and nuclear is a critical to Democrats’ climate strategy.

“I see the [clean electricity program] as the lynchpin or the foundation piece for this bold action on climate,” Democratic Sen. Tina Smith, who is a lead proponent of the provision, told CNN.

The bill also contains measures to create a job-generating Civilian Climate Corps; tax credits and grants for clean energy, renewables and electric vehicles; new polluter fees for methane and carbon; and consumer rebates to electrify and weatherize homes. What is yet to be finalized is how much funding each program gets.

Schumer’s office recently put out an analysis showing the bipartisan infrastructure bill and $3.5 trillion budget bill combined could meet the majority of Biden’s target to slash emissions by the end of the decade — putting the US on track to reduce its greenhouse gas emissions by approximately 45% below 2005 levels by 2030.

“When you add administrative actions being planned by the Biden Administration and many states — like New York, California, and Hawaii — we will hit our 50% target by 2030,” Schumer wrote in a letter accompanying the analysis.

An uncertain future

Democratic leaders have promised a two-track strategy of advancing the budget and bipartisan infrastructure bill together. They want to pass both in the House by the end of September, which will be a monumental task, as moderate and progressive Democrats have already started jockeying over the price tag.

While moderates want to see a smaller bill, House progressives want to go bigger and add more money added for climate, and they plan to withhold their votes for the bipartisan infrastructure bill to do it.

“I don’t know if $3.5 trillion as a top line is going to be enough to deal with the scale of the crisis,” Rep. Jamal Bowman of New York recently told CNN. “I’m considering withholding my vote for reconciliation if it is not big enough and if it doesn’t meet the scale of the problem.”

With moderates and liberals squaring off, Democratic leaders Schumer and House Speaker Nancy Pelosi can afford few Democratic defections in the House, and none in the Senate.

“The stakes are high, the task is enormous, the congressional majorities are quite literally as thin as they could be,” said Sam Ricketts, co-founder of the climate policy group Evergreen and a former top climate staffer for Washington Gov. Jay Inslee. “The Biden administration’s climate commitments are going to live or die with the success of robust investments through legislative action.”