Presidential hopeful Joe Biden celebrates a victory in South Carolina.Credit: Scott Olson/Getty

A key debate on climate change is coming into focus for November’s US presidential election. Voting this week in Michigan and several other states has cemented former vice-president Joe Biden’s lead over Bernie Sanders as the person to take on President Donald Trump in November.

Although both Biden and Sanders, a senator from Vermont, have embraced the idea of a ‘green new deal’ to address the challenge of global warming, their proposed policies are worlds apart. Meanwhile, Republican leaders, seeing the rise of public support for action on climate change, are beginning to discuss the need to devise their own strategies.

Although the escalating issues with COVID-19 could take centre stage, climate policy still could have its largest role yet in a US presidential election, says David Victor, a political scientist at the University of California, San Diego. “The Democratic base is fired up and fed up,” Victor says.

“I think this is a pivotal moment for the climate effort, right here right now,” says former Republican congressman Bob Inglis, who heads the Energy and Enterprise Initiative, a think tank that advocates politically conservative environmental solutions at George Mason University in Fairfax, Virginia. If Democrats had embraced Sanders’s vision of how to solve the climate problem, he argues, it would have alienated conservatives and set back the climate cause. “We appear to have dodged a bullet,” Inglis says.

Whose deal?

Sanders, who describes himself as a democratic socialist, envisions the government taking charge of the energy system and investing more than US$16 trillion to ramp up renewable energy. The plan would aim to eliminate emissions from electricity generation and transport by 2030, and achieve carbon neutrality by mid-century. According to Sanders, the effort would address poverty and inequality by creating 20 million jobs, and it would be paid for in part by taxes and fees levied on wealthy individuals and corporations, in particular the fossil-fuel industry.

His plan raised eyebrows among political scientists, who say it would be impossible to get it through Congress, and among economists, who say it would be unnecessarily expensive. Biden’s plans are less clear, but he too has promised to put the United States on a course to carbon neutrality by 2050. He talks about investing in clean-energy innovation, incentivizing the deployment of low-carbon technologies and advancing regulations on greenhouse-gas emissions — programmes that would revive and extend the policies of former president Barack Obama. Biden has also said he supports a federal carbon tax, which Sanders has rejected as insufficient.

A first step for any future Democratic president would be to rejoin the 2015 Paris climate accord and restore climate rules and regulations that Trump has been busy repealing, says Jody Freeman, an environmental-law specialist at the Harvard Law School in Cambridge, Massachusetts, and a former White House adviser under Obama.

Wild card

Conservatives are also feeling the pressure. Businesses are increasingly calling for a coordinated federal climate policy, and Republican leaders have begun talking about plans. Even Trump, whose administration has been openly hostile to climate policies of any kind, has endorsed the idea of planting trees to pull carbon dioxide out of the atmosphere.

“The party is at risk of haemorrhaging younger voters on climate,” says Ted Halstead, chair of the Climate Leadership Council, a bipartisan climate coalition including senior Republican politicians, environmental groups and major corporations — among them oil companies such as BP and ExxonMobil.

In February, this group released a detailed outline of its proposal, which centres on a tax-and-dividend programme that would put a price on greenhouse-gas emissions and return the revenue to the public. The tax would start at $40 per tonne of carbon dioxide and go up 5–10% annually as needed to meet the target of halving energy-related carbon emissions by 2035. A US family of four could start receiving dividend cheques of around $2,000 in the first year.

The plan has backing from the corporate sector and follows an approach that should appeal to conservative Republicans, says Halstead. Roberton Williams, an economist at the University of Maryland, College Park, who carried out the economic modelling on the proposal, says it is also the easiest, most cost-effective way to drive down emissions.

But even with pressure from voters mounting, many observers are sceptical about whether the current generation of Republicans — who have overwhelmingly opposed climate policies and often denied the veracity of the underlying science — will actually raise their hands and vote for a massive carbon tax.

“I remain dubious,” says Sam Ricketts, a senior fellow at the Center for American Progress, a progressive think tank in Washington DC. If Biden is elected, Ricketts says, he might have to develop a broader agenda on less controversial fronts, including green infrastructure and jobs programmes that run alongside aggressive new clean-energy requirements

But first, he needs votes. Victor says Biden's next challenge will be to bring Sanders’s supporters on board and make sure they don't sit out the election in protest. One way to do that is to flesh out his policies and make it clear that climate change is a top priority, Ricketts says. “This is an opportunity for him to speak to the progressives and young voters.”