WASHINGTON, Jan 20 (AFP) — Joe Biden has said he will return the United States to the Paris climate accord as soon as he takes office, and is also widely expected to block an oil pipeline project in a move that threatens to strain ties with Canada.

And that's just the start. 

Experts say that after four years under Donald Trump, the Democrat will have to rebuild the credibility the US lost in the eyes of the international community, by setting concrete goals for its emissions reductions on the path to net zero by 2050.

Next, he'll need to realize his $2 trillion climate plan, which would place green action at the heart of the economy and its recovery from the Covid-19 pandemic, to ensure a long term shift that can't be rapidly undone under any future Republican president.

"I think it's important that the US shows that it means businesses at home," David Waskow of the World Resources Institute told AFP.

The WRI is advocating for the US to set a 45-50 percent reduction in total greenhouse gas emissions by 2030 compared to 2005 levels.

Biden has also vowed to convene the leaders of major economies for a climate summit within 100 days of his inauguration on Wednesday. 

There are a number of possible steps the incoming leader could take right away to roll back environmental harms done by his predecessor.

These include reentering the Paris agreement — a 30-day process that begins when the US sends a letter to the UN — and scrapping the Keystone XL pipeline connecting the Alberta oil sands to coastal refineries in Texas.

The federal government has additional tools at its disposal, with Biden campaign spokesman Jamal Brown telling Vox that the incoming administration will move to impose strict methane limits on new oil and gas infrastructure.

Federal contracts will also be geared toward renewable energy in infrastructure, and zero-emissions vehicles.

The Trump administration took an axe to a host of environmental regulations — from car emissions standards to industrial air pollution, which Biden can quickly undo, while unveiling new standards like protecting 30 percent of America's land and water by 2030.

While former secretary of state John Kerry will lead US climate negotiations abroad, the domestic front will be headed up by Gina McCarthy who Biden has picked as the first national climate adviser.

Infrastructure plan

Biden will present to Congress next month an infrastructure-focused "Build Back Better Recovery Plan" — separate from the $1.9 trillion Covid package he's seeking.

This is where things can potentially become more tricky, given the Democratic Party's razor thin control of the Senate.

The package is expected to be similar to the $2 trillion green climate plan Biden outlined during his campaign.

It promises "to meet the climate crisis, build a clean energy economy, address environmental injustice, and create millions of good-paying union jobs" — in other words the "Green New Deal" in concept, if not specifically in name.

"The challenge will be to bring Republicans on board with a clean energy infrastructure package that could systematically reduce American emissions," Paul Bledsoe, a climate adviser to former president Bill Clinton now with the Progressive Policy Institute told AFP.

Bledsoe predicted Biden will initially be expected to try to work with Republican colleagues to reach the 60-vote threshold required to pass most legislation — though if that doesn't pan out there are processes to pass laws with a simple 51-vote majority.

"Embedding climate action fully into the way in which we build the economy, the way in which we generate jobs and ensure an equitable recovery, all of that is what will make this something long lasting," said Waskow.

The political and technical challenges are great, and there will be pressure on Biden not to cut fossil fuels loose too quickly — particularly natural gas, which has helped the US lower its net emissions for a decade and is seen as a crucial "bridging" energy.

But it also comes at a time of record-high recognition of climate change and desire for action among the US public.

A survey conducted after the election and published last week by the Yale Program on Climate Change Communication found a majority of voters from both parties support policies to reduce carbon pollution and promote clean energy.

Fifty-three percent of voters said that global warming should be a high or very high priority for the president and Congress, while 66 percent said that developing sources of clean energy should be a high or very high priority.