The alarm bells are ringing. A code red has been declared. With no less than the future of the planet at stake, Kathy Castor, chair of the select committee on the climate crisis, has warned Democrats that there is precious little time left to enact the US president’s aggressive climate agenda and avert the most catastrophic impacts of global warming.

“We just don’t have any more time to waste,” the Florida congresswoman said in an interview with the Guardian ahead of crucial UN climate talks in Scotland. “We have got to act now or else we’re condemning our children and future generations to a really horrendous time.”

Climate scientists say the world must keep the average global temperature from rising more than 1.5C (2.7F) compared with the pre-industrial era, or risk catastrophically more dangerous effects of climate change. Upon rejoining the global effort to confront the climate crisis, Joe Biden vowed that the US would cut emissions by 50% to 52% below 2005 levels by the end of the decade.

Perhaps the best hope of achieving that goal is embedded in legislation pending before Congress that must overcome the objections of a coal-state senator and razor-thin Democratic majorities. If enacted, Castor said the plan to slash planet-heating emissions by accelerating America’s transition away from fossil fuels would be “the most important and far-reaching clean energy and climate bill ever passed by the US Congress”.

But with days left before Biden is expected to depart for the summit, significant obstacles remain.

Senator Joe Manchin, one of the party’s last remaining holdouts, made clear that he would not support a proposed clean electricity program, effectively gutting the most powerful piece of Democrats’ climate plan. The $150bn proposal, known as the Clean Electricity Performance Program, used a carrot-and-stick approach to reward energy utilities that transitioned from coal and natural gas toward clean power sources like wind, solar and nuclear energy, and penalizing those that do not.

Now White House officials and congressional negotiators are scrambling to salvage pieces of the plan while finding alternative policies that will keep the US on track to meet the president’s emissions targets, including, potentially, a tax on carbon dioxide pollution.

“It’s clear that investing in clean electricity is one of the most effective ways to unlock emission reductions and create good-paying jobs across our economy, which is why we’ve fought to include a robust Clean Electricity Performance Program in the Build Back Better Act,” Castor said in a statement following news of Manchin’s objection to the program. “Every step we take now to clean up our electricity sector will make a world of difference in the decades to come – and we cannot afford to keep kicking the can down the road.”

After the Democratic takeover of the House in 2018, Castor was tapped to lead the newly created House select committee on the climate crisis. Its task was to conduct research and hearings that would educate the public about the threat posed by climate change and pave the way for mitigation legislation.

Last year, the panel’s Democratic members released a sprawling climate plan that aimed to put the nation on the path to achieving net-zero greenhouse gas emissions by 2050. It also aimed to make environmental justice a priority by focusing on the communities that are the most vulnerable to climate change.

A summer of devastating heatwaves, wildfires and hurricanes has made the risk of inaction painfully clear to Americans across the country, Castor said, speaking from Tampa, Florida, where rising sea levels are no longer a threat but a costly reality for many residents.

“When you have farmers whose crops or livestock have been flooded out or dropping from an extreme heat, or wildfires are burning through your town, or your electric grid isn’t resilient and people die in Texas because of a cold snap, that’s a wake-up call,” Castor said. “And I think now people are really looking at policymakers and asking, ‘What are you going to do about it?’”

Republicans remain a chief obstacle to Democrats’ climate goals.

After years of denialism, there is a growing acceptance of climate science among rank-and-file Republicans, particularly those representing frontline districts battered by climate-fueled disasters. And yet, the party remains largely opposed to plans to stop burning fossil fuels, which climate scientists say is the most efficient and effective strategy to guard against an even hotter planet.

Castor said Republicans are missing a once-in-a-generation economic opportunity. Democrats have touted the transition to clean energy as an economic boon, with the president repeatedly promising “jobs, jobs, jobs”.

“As clean energy grows in districts across the country, you’ll see more Republicans finally understanding it creates jobs and is less costly for the folks they represent,” Castor predicted. “That’s kind of the only pathway out of the trap they’ve gotten themselves into – to talk about climate but not do anything about it.”

Democrats face a difficult electoral map in 2022, with their control of both chambers at risk. Many activists and Democratic lawmakers believe they have one, perhaps fleeting, chance to aggressively confront climate change before possibly losing their majorities to Republicans, who are far less likely to act on the crisis.

Castor believes that the Democrats’ spending bill cannot be the last legislative action taken by this Congress. But she is less concerned by the political deadline than the scientific one.

Despite the difficulty of finding a consensus among Democrats on climate legislation, Castor believes there is more Congress can do this term. As an example, she pointed to a funding bill passed by the House that aims to minimize the carbon footprint of the Department of Defense, by making military bases more resilient and bolstering investments in research to better understand the security implications posed by climate change.

At the same time, she expects the president will continue to use his executive authority and the rule-making powers of the Environmental Protection Agency to combat climate change.

“We’ll have a lot more to do,” she said. “Even if we pass the Build Back Better Act as it is, that doesn’t really get us to net zero by 2050, which is the goal.”

Democrats are increasingly optimistic that they will send Biden to Glasgow with an agreement that proves the US is capable of making good on its climate promises. How Democrats accomplish this – and whether they can do it by 31 October, when the summit is due to begin – is unclear.