After four years on the sidelines, John Kerry is getting back into politics to combat climate change.

“America will soon have a government that treats the climate crisis as the urgent national security threat it is,” the former secretary of state and former longtime senator from Massachusetts tweeted on Monday after President-elect Joe Biden announced he’ll name Kerry as the incoming administration’s presidential envoy for climate.

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Kerry “will fight climate change full-time as Special Presidential Envoy for Climate and will sit on the National Security Council,” read a statement from Biden’s transition team.

FILE - In this Feb. 1, 2020, file photo Democratic presidential candidate former Vice President Joe Biden smiles as former Secretary of State John Kerry, left, takes the podium to speak at a campaign stop at the South Slope Community Center in North Liberty, Iowa. (AP Photo/Andrew Harnik, File)

FILE - In this Feb. 1, 2020, file photo Democratic presidential candidate former Vice President Joe Biden smiles as former Secretary of State John Kerry, left, takes the podium to speak at a campaign stop at the South Slope Community Center in North Liberty, Iowa. (AP Photo/Andrew Harnik, File)

Biden's move puts a spotlight on his commitment to elevate the issue of climate change in his administration. The president-elect, who emphasized throughout his White House run his commitment to combat climate change, said soon after this month’s election that “the battle to save the climate” was among his top five priorities.

Kerry, as secretary of state during President Obama’s second term, was a key member of the team that hammered out the Paris Climate Accord. President Trump, in his first year in the White House, pledged to pull the U.S. out of the global agreement, and that move was finalized earlier this month. The president reiterated this past weekend during the G20 summit that the accord was designed to “kill the American economy” rather than protect the environment.

Biden, as a candidate and now as president-elect, has pledged to return the U.S. to the accord on day one of his presidency.

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Biden’s transition team highlighted that “Secretary Kerry elevated environmental challenges as diplomatic priorities, from oceans to hydrofluorocarbons. He was a key architect of the Paris Climate Accord, and signed the historic agreement to reduce carbon emissions with his granddaughter on his lap.”

Kerry wrote on Twitter that “I'm proud to partner with the President-elect, our allies, and the young leaders of the climate movement to take on this crisis as the President's Climate Envoy.”

Kerry, the 2004 Democratic presidential nominee who narrowly lost his bid for the White House to Republican President George W. Bush, briefly mulled another presidential run in the 2020 cycle. But he soon became a leading supporter and surrogate for Biden during the Democratic primaries. After Biden became the party’s presumptive presidential nominee, the former vice president and his final rival, progressive Sen. Bernie Sanders of Vermont, set up unity task forces on key policy agenda. Kerry co-chaired the climate change task force alongside progressive Rep. Alexandria Ocasio-Cortez of New York.

Justice Democrats, a progressive group allied with both Sanders and Ocasio-Cortez, said in a statement that “we are encouraged by Joe Biden making one of his first major appointments John Kerry as Climate Czar as it demonstrates the urgency of taking bold, global action on the climate crisis.” But the group added that “America also needs a domestically-focused Climate Czar.”

The Sunrise Movement, a progressive group that advocates for political action to combat climate change, called Kerry’s announcement “an encouraging sign of President-Elect Biden’s commitment to addressing the climate crisis” and said they “applaud President-elect Biden for making history with this appointment and congratulate Secretary John Kerry.”

But the group joined with Justice Democrats in adding that “the next White House must also include a counterpart reporting directly to the President to lead an Office of Climate Mobilization, who can marshal, convene, and push federal agencies, departments, states & local governments, industry, and civil society to use every tool at their disposal to address the climate crisis.”

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Fox News' Jacqui Heinrich and Patrick Ward contributed to this report.