Brazil is back, president-elect Luiz Inácio Lula da Silva has told rapturous crowds at the UN climate summit COP27 in Egypt.
Walking into a room of supporters singing his name, Lula promised to restore the Amazon rainforest and chase down climate criminals.
Huge numbers gathered to see him speak, making him one of the superstars of this summit.
Nations are meeting in Sharm el-Sheikh to discuss tackling climate change.
Just two weeks after his narrow election win, Lula is making his first appearance on the international stage, meeting leaders including from the US, China and the EU at the climate conference.
"We must stop this rush to the abyss. There is no climate security for the world without a protected Amazon," he said, saying climate change would have the highest priority for his government.
"We will do whatever it takes to have zero deforestation and the degradation of our biomes."
While there is no doubt Brazil's president is full of ambition when it comes to tackling climate change, analysts say the challenge will be to make these promises come true.
Brazil is deeply divided over Lula's return to power and his job to unite the country won't be easy.
The president told the summit that Brazil would prove that it was possible to generate wealth without destroying the environment, saying it was impossible to separate tackling global warming from poverty.
Striking a harder tone, he said Brazil would ensure that developing nations got the money they are owed to deal with the effects of climate change.
He also pledged to protect indigenous people, whose land has been targeted under current President Jair Bolsonaro. Indigenous people in traditional dress stood up cheering and shaking maracas.
But Lula faces an uphill battle at home in Brazil where he faces significant opposition in Congress and a divided society.
Under Mr Bolsonaro, who will hand over power to Lula in January, deforestation of the Amazon reached record highs.
Puyr Tembé, an indigenous leader from heavily deforested Pará state, told BBC News that Mr Bolsonaro completely dismantled laws protecting the Amazon.
On Tuesday US climate envoy John Kerry said he was confident Lula would bring a complete turnaround on Brazil's approach to the environment.
Former environment minister in Brazil Isabella Teixeira told BBC News that "the world" is now "embracing Brazil at COP27".
Reflecting the challenges at home, Lula told the summit there was just one Brazil and he would govern for all.
In order to make progress on his agenda, Ms Teixeira said Lula would need to convince people and Congress members to agree, not disagree with each other.
Lula must reverse Mr Bolsonaro's legacy by rebuilding the environmental protection agencies, unfreezing the Amazon Fund which promotes conservation, and tackling criminals in the Amazon, according to Marcio Astrini, executive secretary of Brazil's Climate Observatory network.
He says that civil society will not hesitate to challenge the new government it if fails to keep its promises.
"When the government is succeeding, we will support them, but if it fails, we will criticise them."
But Brazil and the world must be prepared for "mistakes and failures", suggests Roberto Waack, a business leader and chair of Arapyaú Institute.
"Climate a complicated problem, Lula has ambitious pledges and we will face disappointments because of the political situation in Brazil," he said.
"You can't just say stop deforestation and the next day the problem is solved," he said.
On Tuesday, young Brazilian activists at COP27 met Lula. "It was hugely emotional, I cried a lot. It is unbelievable to feel part of Brazil again," Gabrielle Alves, an environmental racism researcher who is part of the Clima de Mudança coalition, told BBC News.
Behind the scenes, negotiations between nations are ongoing at COP27 with a final agreement expected on Friday or Saturday.
However there are still wide divisions between countries on key issues.
The question of who will pay the bill for irreversible climate damage remains hotly debated, as developing countries want finance urgently earmarked to cover their losses.
But developed nations are resisting any question of compensation from countries who historically caused the majority of emissions.
There is concern too that the crucial aim to limiting temperature rise to 1.5C - which scientists say is crucial to avoiding the worst effects of climate change - is in jeopardy.