John Kerry, the U.S. special envoy on climate, is stepping down from the Biden administration in the coming weeks, according to two people familiar with his plans.

Kerry, a longtime senator and secretary of state, was tapped shortly after Joe Biden’s November 2020 election to take on the new role created specifically to fight climate change on behalf of the administration on the global stage.

Kerry’s departure plans were first reported Saturday by Axios.

Kerry was one of the leading drafters of the 2015 Paris climate accords and came into the role with significant experience abroad, as secretary of state during the Obama administration and from nearly three decades as a member of the Senate Foreign Relations Committee. Biden’s decision to tap Kerry for the post was seen as one way the incoming president was making good on his campaign pledge to battle climate change in a more forceful and visible manner than in previous administrations.

“The climate crisis is a universal threat to humankind and we all have a responsibility to deal with it as rapidly as we can,” Kerry said in a visit to Beijing last summer, when he met with Vice President Han Zheng on climate matters.

At international climate summits, Kerry always kept a breakneck pace, going from one meeting to another, with world leaders, major business figures and scientists, all interspersed with one press conference after another — to share what he just learned, announce an initiative, or say a few words as civil groups announced their own plans to help combat climate change, thus lending his credibility and weight.

In the span of an hour, at one meeting Kerry would talk in detail about the need for oil companies to drastically reduce methane, a powerful greenhouse gas, then go to another gathering and detail his latest idea to help pay for green energy transition in developing countries and then, some minutes later, go into a long explanation of illegal fishing around the world while attending an event with leaders of Pacific Island nations.

“John Kerry’s tireless work to deliver global progress on the climate crisis has been heroic,” former Vice President Al Gore, who has focused primarily on climate in his post-public office life, said in a statement Saturday. “He has approached this challenge with bold vision, resolute determination, and the urgency that this crisis demands. For that the U.S. and the whole world owe him a huge debt of gratitude.”

While his gravitas has made him a central climate figure around the world, Kerry also has strong critics who argue America’s climate policies don’t amount to leadership in fighting global warming. The Inflation Reduction Act, the largest climate law in U.S. history, is pumping billions of dollars into renewable energies. But many facets of the law emphasize domestic production, thus leading other nations to complain that the law is protectionist and detrimental to their own green industries.

And for years, the United States opposed the creation of a “loss and damage” fund that would see rich nations contribute billions of dollars to help developing countries, often hit hard by extreme weather events driven by climate change. During COP27 in Egypt in 2022, the fund was approved, as the U.S. and other rich countries relented and supported it. However, Kerry is always quick to say the fund is not about “reparations” or “compensation,” and so far the U.S. has promised only modest funding for it.

Kerry represented Massachusetts for 28 years in the Senate and was also the Democratic presidential nominee in 2004.