UNITED NATIONS — Leaders promised the United Nations at the Climate Action Summit on Monday to do more to prevent a warming world.

Secretary-General Antonio Guterres concluded the summit by listing 77 countries that committed to carbon neutrality by 2050, 70 nations pledging to do more to fight climate change, with 100 business leaders promising to join the green economy and one-third of the global banking sector signing up to green goals.

“Action by action, the tide is turning,” he said. “But we have a long way to go.”

Businesses and charities also got in on the act. Microsoft founder Bill Gates announced Monday that his foundation, along with The World Bank and some European governments, would provide $790 million to help to 300 million of the world’s small farmers adapt to climate change. The Gates foundation pledged $310 million of that.

“The world can still prevent the absolute worst effects of climate change by reducing greenhouse gas emissions and developing new technologies and sources of energy,” Gates said. “But the effects of rising temperatures are already under way.”

Before world leaders made their promises in three-minute speeches, the 16-year-old climate activist Greta Thunberg gave an emotional appeal in which she scolded the leaders with her repeated phrase, “How dare you.”

“This is all wrong. I shouldn’t be up here,” said Thunberg, who began a lone protest outside the Swedish parliament more than a year ago. “I should be back in school on the other side of the ocean. Yet you have come to us young people for hope. How dare you. You have stolen my dreams and my childhood with your empty words.”

“We are in the beginning of a mass extinction and yet all you can talk about is money,” Thunberg said. “You are failing us.”

Later, she and 15 other youth activists filed a formal complaint with an arm of the U.N. that protects children, saying that governments’ lack of action on warming is violating their basic rights.

Of all the countries that came up short, World Resources Institute Vice President Helen Mountford said one stood out: the United States for “not coming to the table and engaging.”

“What we’ve seen so far is not the kind of climate leadership we need from the major economies,” Mountford said. She did say, however, that businesses, as well as small- and medium-sized countries had “exciting initiatives.”

Nations such as Finland and Germany promised to ban coal within a decade. Several also mentioned goals of climate neutrality, when a country is not adding more heat-trapping carbon to the air than is being removed by plants and perhaps technology, by 2050.

U.S. President Donald Trump dropped by the summit, listened to German Chancellor Angela Merkel make detailed pledges including going coal-free and left without saying anything.

The United States did not ask to speak at the summit, U.N. officials said. Guterres had told countries they couldn’t be on the agenda without making bold new proposals.