The past years have been a troubled time for the United States in matters of climate protection policy. President Donald Trump repeatedly denied the science on climate change, and his 2017 plan to withdraw the United States from the Paris Agreement came into effect the day after the US presidential election in November 2020.

Joe Biden has pledged that his inauguration would mark a sea change for climate policy. The Democratic Party can expect to have effective control of both houses of the US Congress from January 20, allowing him more power to push his climate agenda.

But what has he promised — and can he make it happen?

Can the US be climate-neutral by 2050?

Matching the goal of the European Union and many other large global emitters, Biden has pledged to make the US climate-neutral by 2050 or earlier — something the environmental economist Nat Keohane describes as a "huge step." Keohane serves as the senior vice president for climate with the US-based global NGO the Environmental Defense Fund (EDF). 

"We are on the cusp of having the world's main three emitters — the EU, China and now the US — having made either climate-neutral or carbon-neutral pledges by 2050 and 2060," Keohane said. Climate neutrality refers to net-zero emissions of all greenhouse gases; and carbon-neutrality specifically refers to net-zero emissions of carbon dioxide (CO2) into the atmosphere.

Though much of Biden's plan to reach this remains a closely guarded secret, Keohane believes that a 50% cut in emissions over 2005 levels by 2030 should be the new administration's first goal.

Christoph Bertram, a German scientist who leads international climate policy analysis in the Energy Systems Group at the Potsdam Institute for Climate Impact Research (PIK), regards the 2050 target as a positive "signal."

"But, for a long-term target like this, there is no single action you could take today that would ensure this goal," Bertram said. "For political purposes it is important to signal to fellow policymakers and other parts of society that you have a clear long-term vision of where things have to go."

What can Biden do domestically during his term?

With 2050 a long way off, all eyes are on what Biden does at home in the next few years.

Key among his domestic climate pledges is his plan to make the US power sector climate neutral by 2035. Bertram said "this is something where there could be visible results within three to four years [in Biden's term]."

In addition to the power sector, Keohane said, the EDF has identified two other key short-term goals for Biden's domestic policy: transportation, particularly with legislation around tailpipe standards for cars and trucks, and methane reduction in industry.

"The federal government needs to go all out on existing authorities like the Clean Air Act," Keohane said. "Methane is the main cause of near-term warming, and reducing that is something Biden can do from day one."

In the US, the oil and gas industries were responsible for 31% of methane production in the US between 1990 and 2017, according to the Environmental Protection Agency — second only to agriculture. Investing in clean energy sources and creating a transition away from these industries will be important in reducing methane emissions in the next few years.

Will the US rejoin the Paris Agreement?

Biden has promised to rejoin the Paris Agreement "immediately" upon taking office. The 2015 treaty sets out a framework for countries to limit global warming to well below 2 degrees Celsius (3.6 F) above preindustrial levels.

"The Paris Agreement is very peculiar: It has common long-term targets, but the mechanism gives a lot of autonomy to nation states by allowing them to determine their own Nationally Determined Contributions (NDCs)," Bertram said.

These NDCs have to be laid out every five years. The US will need to issue its latest NDCs by November this year, ahead of the UN climate conference, COP26.

Rachel Cleetus, policy director at the Climate and Energy Program of the Union of Concerned Scientists, a US-based nonprofit science advocacy organization, described Trump's pulling the United States out of the Paris Agreement as "very shameful." She said the US's new NDC would have to show a willingness to commit.

"It's not enough to just rejoin, [the US] needs to rejoin with clear ambitions on cutting our heat-trapping emissions, as well as providing climate finance to developing countries — in line with our fair share contribution," Cleetus said.

Can the US become a leader on climate?

After four years of "America First," Biden has pledged to "rally the rest of the world to meet the threat of climate change." 

Although there is now a big international trust deficit, there is always a leadership role for the United States, said Keohane, who also worked as a special assistant for energy and environment under President Barack Obama.

Keohane said the United States "needs to start walking the walk at home" with domestic policies. "This is something we can act on relatively quickly," he said.

Cleetus said the Biden administration would have to do a lot more than "trot out the tired rhetoric" about US leadership. 

"What the world needs from the US is not rhetoric but action," she said. "We need to take our place at the table, and do our part responsibly, fairly and quickly."

Bertram said it was "realistic" that the United States could take on a leadership role in climate protection, pointing out that, despite a dearth of federal engagement in climate policies under Trump, many states have pushed ahead with technological innovation and environment policies.

"Some US states see their role as being one of global technological pioneers, and there has been a lot of climate technological progress in the last four years," he said, giving examples of innovations in electric transportation and renewable energy.

Biden's ambitious plans offer the opportunity for the country to go a lot further. How they progress will be of great interest to many.

"We'll be watching closely what he does in his first hundred days, and even on day one," Rachel Cleetus added. "That will make all the difference."