Thunberg bemoans climate inaction

Youth climate activists Greta Thunberg and Vanessa Nakate have chastised global leaders for failing to meet funding pledges and for delivering too much "blah blah blah" as climate change wreaks havoc around the world.

The activists even cast doubt on the intentions behind the youth climate gathering in Milan, where they were speaking.

Four hundred climate activists from 180 countries were invited to Italy's financial capital for a three-day Youth4Climate summit that will send its recommendations to Cop26, a major United Nations climate summit in Glasgow that begins on October 31.

Participants at the Milan summit are demanding more accountability from leaders as well as a bigger official role for young people.

Swedish activist Thunberg said: "They invite cherry-picked young people to pretend they are listening to us.

"But they are not. They are clearly not listening to us. Just look at the numbers. Emissions are still rising. The science doesn't lie.

"Leaders like to say: 'We can do it.' They obviously don't mean it. But we do."

Nakate, a 24-year-old activist from Uganda, said pledges of 100 billion euro ($A161 billion) a year to help countries particularly vulnerable to the impact of climate change had not materialised, even as wildfires in California and Greece and floods in Germany and Belgium show that "loss and damage is now possible everywhere".

"No more empty conferences. It's time to show us the money. It's time, it's time, it's time. And don't forget to listen to the most affected people and areas," she said

Nakate dramatically underlined how climate change is affecting the African continent, "which is ironic given that Africa is the lowest emitter of CO2 emissions of any continent except Antarctica".

Just last week, she said she saw police taking away a body that had been washed away by violent storms in the Ugandan capital of Kampala, while others searched for more victims.

Nakate was comforted by Thunberg after collapsing in tears after her emotional speech.

Thunberg, who coalesced the global protest movement Fridays for Future, insisted it was not too late to reverse climate trends.

However, she has clearly heard enough from leaders, whom she said have been talking for 30 years while half of all carbon emissions have occurred since 1990 - and one third since 2005.

"Our hopes and dreams drown in their empty words and promises. Of course we need constructive dialogue, but they have now had 30 years of blah, blah, blah. And where has this led us?" Thunberg said.

The three-day Youth4Climate Summit will be followed by a two-day pre-Cop26 meeting before Glasgow.

Hopes for a successful Glasgow summit have been boosted by announcements from the world's two biggest economies and largest carbon polluters, the United States and China.

Chinese President Xi Jinping said his country would no longer fund coal-fired plants abroad; his US counterpart Joe Biden plans to double financial aid for green growth to poorer nations.