Greta Thunberg branded the UN climate talks in Glasgow so far "a failure," accusing leaders of actively creating loopholes in the rules and greenwashing their countries' emissions.
Speaking at a rally outside the conference venue, Thunberg called for tougher rules to clamp down on polluters instead of what she termed "distant, non-binding pledges."
"World leaders are obviously scared of the truth, yet no matter how hard they try, they cannot escape it," she said. "They cannot ignore the scientific consensus, and above all they cannot ignore us - the people, including their own children."
Developed nations will start making good on their joint pledge of $100 billion in annual climate aid to developing nations next year, US climate envoy John Kerry said Friday.
That's at least a year earlier than some estimates. "So there is genuine progress," Kerry told reporters at a press conference, listing advancements that have moved climate efforts forward over the past year.
The United States and other developed nations committed to the financing pledge under the landmark 2015 Paris climate accord.
Less wealthy countries say they cannot switch their economies to cleaner fuel, and protect their people from increasing natural disasters as the Earth warms, without substantial foreign aid.
And they say established economies, like the United States, should pay, since they historically have been responsible for most of the climate damage from burning coal and petroleum.
Former US Vice President Al Gore has compared the world's complacency on climate change to the way it failed to take seriously the threat of fascism during the 1930s.
Invoking Winston Churchill's famous warning that "the era of procrastination is coming to its close," Gore told the UN climate summit in Glasgow that the impacts of global warming would soon spur momentum for action.
"We are now experiencing the consequences of the climate crisis in every part of our world," he said Friday, echoing Churchill. "The scientists warned us that these consequences were coming."
Gore starred in "An Inconvenient Truth," an Oscar-winning 2006 documentary about the threat of climate change.
In Glasgow, he praised countries and companies that recently made new pledges to curb emissions but added that the fulfillment of those commitments must be closely watched.
Gore advocated for "radical transparency" that includes monitoring emissions from the ground, the sea, by air and by satellite to identify those responsible for releasing greenhouse gas into the atmosphere.
He also warned that the rising number of climate refugees expected over the coming decades risked triggering "xenophobia and anger" which in turn could fuel authoritarian populism around the world.