John F. Kerry, a former secretary of state, senator and Democratic presidential nominee, will lead the country’s reentry into global climate politics in a new role that will elevate climate change as a priority of President-elect Joe Biden.

As the presidential envoy for climate, Kerry will report directly to Biden as part the White House’s National Security Council, underscoring how the incoming administration views the warming planet as an issue with implications for both national defense and foreign policy.

Kerry “will fight climate change full-time as Special Presidential Envoy for Climate,” according to a statement Monday by Biden’s transition team. “This marks the first time that the NSC will include an official dedicated to climate change, reflecting the president-elect’s commitment to addressing climate change as an urgent national security issue,” the statement said.

Kerry, who played a key role in negotiating the 2015 Paris climate accord as secretary of state during President Barack Obama’s second term, will be on hand to see the United States rejoin the global agreement under Biden. President Trump, who has been skeptical about climate change, withdrew the United States from the international accord, making it the only nation out of nearly 200 signatories to abandon a deal that calls for countries to collectively reduce greenhouse gas emissions.

Kerry, a longtime Biden ally who turns 77 next month, tweeted Monday that he intends to use his new post to tackle the world’s most pressing environmental problem.

“The work we began with the Paris Agreement is far from done,” he said. “I’m returning to government to get America back on track to address the biggest challenge of this generation and those that will follow. The climate crisis demands nothing less than all hands on deck.”

Kerry has continued to work on climate-related issues since the end of the Obama administration.

Last year, Kerry launched World War Zero, a coalition of scientists, celebrities, world leaders and other activists to push for more aggressive climate action around the globe. The group describes its mission as “uniting unlikely allies with one common mission: respond to the climate crisis now.”

Earlier this year, Kerry co-chaired a climate task force with Rep. Alexandria Ocasio-Cortez (D-N.Y.) set up by the Biden campaign to make policy recommendations and bring supporters of Sen. Bernie Sanders (I-Vt.) into the fold after Biden secured the Democratic nomination.

Catherine Coleman Flowers, an environmental activist in Montgomery, Ala., and a Sanders surrogate on the panel, said Kerry helped smooth over disagreements involving nuclear energy and other issues during Zoom meetings.

“He was quite the diplomat in terms of trying to make sure that all sides were represented and that we could reach compromises that we could all live with,” she said. “He had a good understanding of the climate crisis.”

Jason Bordoff, founder of Columbia University’s global energy center and who served as senior director for energy and climate at the National Security Council under Obama, said Biden “didn’t unveil his climate team today; he unveiled his national security team and put his climate envoy in it.”

Appointing someone of Kerry’s stature and inserting that role into the National Security Council “signals Biden’s understanding that climate change is a critical foreign policy issue for the U.S.,” Bordoff said.

In addition to naming Kerry, according to two individuals briefed on the transition’s plans who spoke on the condition of anonymity to discuss private deliberations, the president-elect plans to appoint a high-level White House official to coordinate domestic action on climate throughout the federal government. This official would focus on how to maximize Biden’s executive authority, while looking for legislative opportunities as well, they said. Los Angeles Mayor Eric Garcetti (D) is under consideration but the team is also looking at current members of Congress and others for the job, according to one of these individuals.

Biden has pledged to weave climate action throughout the sprawling federal government, making it a policy consideration beyond the typical environmental agencies at departments such as Treasury and Agriculture.

Kerry has spent much of his career working to avert catastrophic global warming. He has represented the United States at every pivotal international climate conference in the past three decades, including the 1992 Rio Summit that launched the framework for every subsequent global agreement; the one in Kyoto that forged the first international climate treaty in 1997; and the 2009 meeting in Copenhagen. Even in years that were less critical, Kerry traveled to spots ranging from Poland to Bali to convince his international counterparts that the United States was committed to curbing greenhouse gas emissions even if the current White House occupant was not.

In 2010, Kerry and Sens. Joseph I. Lieberman (I-Conn.) and Lindsey O. Graham (R-S.C.) sought unsuccessfully to patch together a climate bill a year after the House passed a bill that would cap carbon pollution nationwide but allow industries to buy and sell emissions credits.

But a decade of rising global temperatures and more frequent wildfires and storms has made slowing climate change more imperative than ever. At least 10 percent of the planet has already seen average temperatures rise more than 1.5 degrees Celsius, compared to preindustrial levels. That’s the threshold beyond which scientists say the environment will suffer irreversible damage in ways that threaten all life on Earth, including humans.

Kerry himself spoke of the need to act decisively as nations worked to finalize the Paris accord in late 2015.

“The science has been warning us for decades, screaming at us,” he said at the time. “And we know also that if we just continue down the current path with too many people sitting on their hands, waiting for someone else to take the responsibility, guess what? The damage is going to increase exponentially.”

“So, to cut to the chase, unless the global community takes bold steps now to transition away from a high-carbon economy, we are facing unthinkable harm to our habitat, our infrastructure, our food production, our water supplies, and potentially to life itself,” he said.

Word of Kerry’s new role Monday prompted quick praise from many foreign and domestic climate advocates, both because of his experience but also because the new role cements climate change as a central priority of the incoming administration.

“This appointment finally elevates climate change to the very center of U.S. national security policy, where it belongs,” Paul Bledsoe, a former climate adviser in the Clinton White House, said in an email. “Secretary Kerry’s stature both at home and abroad instantly signals that Biden intends to make climate change among his Administration’s top domestic and foreign policy priorities.”

Laurence Tubiana, an architect of the 2015 Paris agreement and chief executive of the European Climate Foundation, praised Kerry’s work in helping forge the international accord.

“He fought hard for a fair deal for both the U.S. and the planet,” Tubiana said in a statement. “He understands the challenge we face.”

During the presidential campaign, Biden created a stir by underscoring that the nation would have to start to transition away from fossil fuels. On Monday, the trade associations representing the oil and gas industry said they looked forward to working with Kerry, even if they sought their own solutions.

American Petroleum Institute President Mike Sommers said his group supported “industry-led solutions” and “innovative technologies.” Martin Durbin, president of the U.S. Chamber of Commerce’s Global Energy Institute, said the Chamber sought to “position itself as a positive force” through “meaningful and obtainable policies that would move things forward on climate.”

One key piece of Kerry’s new role, as he alluded to Monday, will be to bring to the federal government a renewed sense of urgency about climate change — partly by reflecting the concerns of young people who have rallied for more immediate, tangible action and who campaigned for Biden this year.

“One thing is clear: he really does care about stopping climate change,” Varshini Prakash, a co-founder of the youth-led Sunrise Movement who served alongside Kerry on the climate task force earlier this year, tweeted Monday. “That’s something we can work with. An encouraging move from the Biden team.”

Dino Grandoni contributed to this report.