In a video address to the United Nations high-level climate summit on Wednesday, Chinese president Xi Jinping told his fellow leaders that the world's second largest economy will finally reduce the emissions of the gases that scientists say cause global warming and extreme weather.
It came as more than 100 world leaders gathered to talk of increased urgency and the need for stronger efforts to curb the spewing of heat-trapping gases.
With major international climate negotiations in Brazil six and a half weeks away, the United Nations Secretary-General Antonio Guterres convened a special leaders summit on Wednesday during the General Assembly to focus on specific plans to curb emissions from coal, oil and natural gas.
Xi pledged that China would increase its wind and solar power sixfold from 2020 levels, make emissions-free vehicles mainstream and "basically establish a climate adaptive society".
Europe then followed with a less detailed and not quite official new climate change fighting plan.
Ursula von der Leyen, president of the European Commission, said their infrastructure and investment in renewable energy and the price of carbon dioxide had all increased, and their emissions are down nearly 40 per cent since 1940.
Last week, member states agreed that their nationally determined contribution would range between 66 per cent and 72 per cent, and that they would formally submit their plan before the November negotiations, she said.
Xi and Brazil's leader on Wednesday afternoon took thinly veiled swipes at US President Donald Trump's opposition a day earlier to renewable energy and the concept of climate change.
"While some country is acting against it, the international community should stay focused on the right direction," Xi said.
Brazilian President Luiz Inácio Lula da Silva, who is hosting the upcoming climate conference, said, "no one is safe from the effect of climate change".
"Walls at borders will not stop droughts or storms," Lula said.
"Nature does not bow down to bombs or warships. No country stands above another."
"All of us may lose because denialism may actually win," he concluded.
Guterres said "the science demands action. The law commands it. The economics compel it. And people are calling for it".
"Warming appears to be accelerating," climate scientist Johan Rockstrom said in a science briefing that started the summit.
"Here we must admit failure. Failure to protect peoples and nations from unmanageable impacts of human-induced climate change."
"We're dangerously close to triggering fundamental and irreversible change," Rockstrom said.
Under the 2015 Paris climate accord, 195 countries are supposed to submit new more stringent five-year plans on how to curb emissions from the burning of coal, oil and natural gas.
Technically the deadline was in February and about 50 countries - responsible for one-quarter of the world's CO2 emissions - have filed theirs, including Pakistan, Micronesia, Mongolia, Liberia and Vanuatu.
All of those countries submitted on Wednesday.
UN officials said countries really need to get their plans in by the end of the month so the world body can calculate how much more warming earth is on track for if countries do what they promise.
Before 2015, the world was on path for 4C of warming since pre-industrial times but now has trimmed that to 2.6C, Guterres said.
However, the Paris accord set a goal of limiting warming to 1.5C since the mid 19th century and the world has already warmed about 1.3C since.
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