Trump-Biden transition: Attorney Sidney Powell back at White House Sunday

Biden introduced his climate and energy team nominees and appointees Saturday in Wilmington, Delaware.

"I'm pleased to announce a team that will lead my administration's ambitious plan to address the existential threat of our time, climate change," the president-elect said in his opening remarks.

Biden highlighted the diversity of his Cabinet picks, noting that his nominee for secretary of the interior, Rep. Deb Haaland, would be the first Native American Cabinet secretary if confirmed by the Senate.

"The Biden-Harris cabinet, it will be historic -- the cabinet that looks like America, that taps into the best of America, that opens doors and includes the full range of talents we have in this nation," Biden said.

The president-elect also stressed the importance of taking on an issue central to his administration.

"We literally have no time to waste," Biden said. "We're in a crisis. Just like we need to be a unified nation in response to COVID-19, we need a unified national response to climate change."

Announcing Haaland as his secretary of the interior nominee, the president-elect said, "The Federal government has long broken promises to Native American tribes who have been on land since time immemorial. With her appointment, Congresswoman Haaland will help me strengthen the nation-to-nation relationship, and I’m honored... she’s been willing, when I called her, to accept this critical role."

For his nominee for energy secretary, Biden highlighted former Gov. Jennifer Granholm's commitment to clean energy and helping the Obama administration bail out the auto industry during the Great Recession.

"(Granholm) bet on the promise of a clean energy future. Her leadership helped rescue the automobile industry in the United States of America, helped save a million American jobs, and helped bring Detroit back," Biden said.

The president-elect also announced North Carolina Department of Environmental Quality Secretary Michael Regan as his nominee for E.P.A. administrator, Regulatory Policy at the Southern Environmental Law Center Director Brenda Mallory as his appointee for chair of the Council on Environmental Quality, former E.P.A Administrator Gina McCarthy as national climate adviser, and New York Deputy Secretary to the Governor for Energy and Environment and Chairman of Climate Policy Ali Zaidi as his deputy national climate adviser.

In November 1972, Joe Biden made headlines as the 29-year-old lawyer who pulled off an upset win against Sen. Caleb Boggs to represent Delaware in the Senate -- one of the youngest people ever elected to the body. But it was a different headline a month after the election that would forever change his life: "Biden's wife, child killed in car crash."

"I was down in Washington hiring staff and I got a phone call from a first responder. They put a pretty young woman on the phone. She was so nervous, she said, 'You gotta come home. There's been an accident. A tractor trailer hit your wife and your three children while they were shopping,'" Biden recalled at a campaign event in Newton, Iowa, last August.

"My wife was killed and my daughter was killed," he continued. "And my two boys, but for the jaws of life, and a rescue crew saving their life, would not have been around either."

Friday morning, on the 48th anniversary of the accident, the president-elect refrained from public events, instead visiting the graves of his late wife, Neilia, and daughter, Naomi, at Brandywine Roman Catholic Church with his wife, Jill, near his home in Wilmington, Delaware.

The anniversary comes, as it did in 1972, as Biden is preparing for a new role in public life -- this time the presidency. The role caps off a lifetime in politics that almost ended before it began. Biden had initially decided to stay in the Senate for only six months following his wife and daughter's deaths and in order to care for his injured sons.

Despite his initial unwillingness to serve, Biden remained in the Senate and public life, turning his grief into a way to connect with others through empathy -- a trait that has perhaps most defined his career.

-ABC News' Molly Nagle

Biden and Vice President-elect Kamala Harris will introduce key nominees and appointees for their climate and energy team Saturday in Wilmington, Delaware.

The nominees and appointees attending the event will include secretary of interior nominee Rep. Deb Haaland, D-N.M.; secretary of energy nominee former Michigan Gov. Jennifer Granholm; E.P.A. administrator nominee Michael Regan; Chair of the Council on Environmental Quality nominee Brenda Mallory; national climate adviser appointee Gina McCarthy and deputy national climate adviser Ali Zaidi.

Asked whether he will join with other House Republicans to formally object to the certification of the Electoral College results on Jan. 6, House Minority Leader Kevin McCarthy, R-Calif., laughed and told reporters, "We'll watch and see," per the pool reporter on Capitol Hill. 

McCarthy hasn't formally taken a position on the long-shot effort, which still lacks Senate Republican support needed to force debate and vote on the results of the election, nor has he recognized Biden as the president-elect.

The Electoral College affirmed Biden's victory on Monday without any faithless electors. Trump won 232 electoral votes to Biden's 306.

-ABC News' Benjamin Siegel