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The United States is hosting 40 world leaders in a two-day virtual summit in the White House to discuss ways of fulfilling the 2015 Paris climate agreement. The US and other countries pledged bigger greenhouse gas emission cuts.
Ardern said New Zealand had been leading the charge on "climate finance" such as ending fossil fuel subsidies.
"Global agreement on the need for fossil fuel subsidy reform is long overdue. Fossil fuel subsidies undo any advances we make on pricing carbon.
"We cannot take money from emitters paying for their carbon emissions and then give them money back in subsidies."
She said the $US500 billion ($NZ767 billion) per year in subsidies could be spent elsewhere.
"Imagine what diverting trillions of mobilised finance could do to help us achieve our collective goal to limit global warming to 1.5 degrees above pre-industrial levels.
"It is time to stop imagining and for us to do what is needed."
Ardern called on leaders to price carbon, make climate-related financial disclosures mandatory, end fossil fuel subsidies, and finance adaptation.
New emissions goals
US President Joe Biden unveiled a goal to cut emissions by 50 to 52 percent from 2005 levels. The cuts are expected to come from power plants, automobiles, and other sectors across the economy, but the White House did not set individual targets for those industries.
Canada Prime Minster Justin Trudeau country's goal to a cut of 40 to 45 percent by 2030 below 2005 levels - up from 30 percent.
Brazil's President Jair Bolsonaro announced his most ambitious environmental goal yet, saying the country would reach emissions neutrality by 2050, 10 years earlier than the previous goal.
Japan's Prime Minister Yoshihide Suga raised his country's target for cutting emissions to 46 percent by 2030, up from 26 percent.
Greenpeace UK's head of climate Kate Blagojevic said the summit had more targets than an archery competition.
"Targets, on their own, won't lead to emissions cuts," she said. "That takes real policy and money. And that's where the whole world is still way off course."
Most of the countries did not offer new emissions goals. Chinese President Xi Jinping said China expects its carbon emissions to peak before 2030 and the country will achieve net zero emissions by 2060.
UN Secretary-General Antonio Guterres called for rich countries to make good on their promises of climate finance for developing nations at the G7 meeting in June.
He noted that global warming had already hit 1.2 degrees Celsius and was "racing toward the threshold of catastrophe".
To get all countries on board to achieve net-zero emissions by mid-century, a "breakthrough" was needed on climate finance and efforts to help communities adapt to the fast-accelerating impacts of global warming, he said.
The summit is the first in a string of meetings of world leaders - including the G7 and G20 - ahead of annual UN climate talks in November in Scotland. That serves as the deadline for nearly 200 countries to update their climate pledges under the Paris agreement, an international accord set in 2015.
World leaders aim to limit global warming to 1.5 degrees Celsius above pre-industrial levels, a threshold scientists say can prevent the worst impacts of climate change.
- RNZ and Reuters