Brazilian President Luiz Inacio Lula da Silva has urged leaders of the Group of 20 major economies to accelerate their national climate targets, calling on them to reach net zero climate emissions five to 10 years ahead of schedule.
Opening the last session of the G20 summit in Rio de Janeiro on Tuesday, Lula suggested countries bring forward their targets to reach climate neutrality by 2040 or 2045, instead of 2050 as Brazil and many others have pledged.
"We have to do more and better," Lula said, noting that this is likely the world's warmest year on record as climate disasters such as flooding and droughts become more frequent and intense.
"There is no time to lose."
World leaders are trying to shore up a global response to climate change before
Donald Trump retakes the US presidency in January, when he plans to roll back US policy on global warming and reportedly exit the landmark Paris Agreement.
G20 nations are seen as vital to shaping the response to global warming, as they account for 85 per cent of the world economy and more than three-quarters of climate-warming emissions.
The G20 leaders called in a joint statement on Monday for "rapidly and substantially increasing climate finance from billions to trillions from all sources" to confront global warming.
They also urged COP29 negotiators to reach a deal on a new financial goal for how much money rich nations must provide to poorer developing nations in climate finance, the main sticking point in the climate talks.
At the G20 summit on Tuesday, when leaders turned their discussion to the environment, Lula urged developing countries to broaden their climate targets to address all emissions that cause global warming, not just from certain sectors or gases.
US President Joe Biden told the gathering that developing countries need to have "enough firepower and access to capital," to slow climate change and protect their countries from its effects. That money needs to flow into their economies and give breathing room to debt-laden countries.
"History is watching us," Biden said.
"I urge us to keep the faith and keep going. This is the single greatest existential threat to humanity."
Lula criticised developed countries for falling short of a promise to deliver $US100 billion ($A153 billion) of climate financing annually to developing countries by 2020.
Lula noted that negotiators at the United Nations COP29 climate summit underway in Baku, Azerbaijan, are pushing for a new global goal of how much wealthier countries should provide to developing nations. Economists suggest the goal should be at least $US1 trillion ($A1.5 trillion) annually.
Those talks, set to conclude on Friday, have bogged down as developed countries call for more countries to contribute toward the goal, while the developing world argues that the rich nations most responsible for climate change need to pay up.
The G20 leaders' statement on Monday said nations must break the impasse on finance, but they did not give clear guidance on a solution.
"G20 leaders have sent a clear message to their negotiators at COP29: do not leave Baku without a successful new finance goal. This is in every country's clear interests," UN climate chief Simon Stiell said in a statement responding to the G20 communique.
The G20 also committed to agreeing on a legally binding treaty to limit plastic pollution by the end of 2024, with talks resuming next week to hammer out a deal two years in the making.
