(Bloomberg) -- President Joe Biden convened world leaders for a two-day virtual climate summit on Thursday to send a message that the U.S. is back and ready to lead. Many of the 40 heads of state who participated had their own message for America: Prove it.Biden opened the event by promising to cut U.S. greenhouse gas emissions by at least 50% below the 2005 levels by 2030, a clear demonstration that climate is at the center of his agenda. That he did so in front of presidents, prime ministers, and a king shows the White House has the influence to draw world leaders together.The summit was also meant to demonstrate a vast difference with former President Donald Trump, who pulled the U.S. out of the Paris Agreement and systematically rejected the threat of climate change. Perhaps the biggest departure came when Biden reappeared to promise a doubling of the U.S. spending towards international climate goals. Annual spending will rise to $5.7 billion by 2024—assuming he can get Congress to go along. Even that, however, may not have been enough to change minds.It’s a sign of how far expectations on climate have shifted in the months since President Trump that these commitments—once unthinkably bold for the U.S.—fell flat with some, particularly leaders of countries most at risk from climate change. Indonesia, for instance, faces devastating flooding in its capital city; its president, Joko Widodo, said that developing nations could consider tightening their emissions targets only if wealthy countries committed to more aid. President Xi Jinping of China also drew attention to the notion of “common but differentiated responsibilities” included in the 2015 Paris climate agreement, which put a greater financial burden on the countries most responsible for global warming.The summit will play very differently inside and outside the U.S., said David Victor, a climate policy expert at University of California at San Diego. Biden is fighting a two-front battle, working to drum up support at home for tough policies and prove to the world he’ll get them. “If you’re back, you need to show that you're back,” he said. “This event was designed to do that, and they did it.”Here are three more takeaways from Day One.1. Biden didn’t get all he hoped forIn the lead-up to the summit, administration officials suggested that their metric of its success would be how many new pledges to reduce greenhouse gases the event inspired. Against that bar, the summit didn’t shine.After weeks of playing coy about whether he would participate in the summit, China’s Xi mostly reiterated his previously announced plans to peak carbon emissions by 2030 and to attain net-zero status by 2060. He did offer one new promise—reducing Chinese coal consumption between 2026 and 2030—but without offering any specifics.Despite aggressive pre-summit diplomacy by U.S. Special Presidential Envoy for Climate John Kerry, only two U.S. allies unveiled new plans to boost previous pledges. Canadian Prime Minister Justin Trudeau raised his nation’s target for greenhouse gas reductions to as much as 45% by 2030, exceeding a previous goal of a 30% reduction from 2005 levels. Japanese Prime Minister Yoshihide Suga raised his country’s target to a 46% reduction by 2030 based on 2013 levels, up from 26% previously (and the the equivalent of a 41% cut based on a 2005 baseline).Kerry acknowledged that expectations were high in a midday press conference, and he classified modest gains as big wins. Twenty of the world’s top polluters had upped their commitments, he said, while appearing to define “commitment” loosely. Kerry cited India Prime Minister Narendra Modi’s move to participate in a new clean energy partnership, for instance, while overlooking that just two weeks ago the climate envoy had traveled to India hoping to persuade Modi to set a net-zero target.On Thursday, however, Modi largely sidestepped new commitments. He focused his remarks instead on his country’s aggressive rollout of clean power generation. India is also facing an aggressive surge in Covid-19, with more than 300,000 new cases a day.Without a major breakthrough, the Earth Day gathering becomes a step towards the all-important United Nations climate conference scheduled for November in the U.K. “The next six months of diplomacy will be absolutely critical to the capacity to make Glasgow what it needs to be,” Kerry said. “I do believe Glasgow remains our last, best hope to be able to coalesce the world in the right direction.”2. Climate finance was a major sore pointIf polluting nations underproduced on climate pledges, wealthy countries may have underwhelmed on financial promises. The U.S. and other rich nations tend to focus on their annual emissions. But China, India, Brazil, and many others maintained that historical emissions are what matters, and that the developed world has much further to go to erase its own carbon legacy.A vocal group of nations used Thursday’s proceedings to demand more money to fund the energy transition. In a briefing after Xi’s remarks, China’s Vice Minister of Foreign Affairs Ma Zhaoxu took a swipe at the U.S. on climate finance. Advanced economies must “take concrete steps to help developing countries raise their capabilities in tackling climate change,” he said, and “avoid setting green trade barriers.”Brazil’s Jair Bolsonaro, meanwhile, advanced his country’s previous position that the country’s climate efforts—including a pledge to end illegal deforestation by 2030—should be explicitly tied to financial assistance from wealthier nations. (His remarks were greeted cynically by many rainforest observers. “Bolsonaro cannot be trusted,” said Leila Salazar-Lopez, executive director of the nonprofit Amazon Watch, in a statement on the speech. “Any agreement with Brazil should be led by civil society and Indigenous and traditional peoples, not Bolsonaro.”)Meeting the U.S.’s new climate finance commitments will require U.S. lawmakers to appropriate the money. The White House confirmed it would ask for $1.25 billion for the UN’s Green Climate Fund, a key piece of the Paris Agreement, while also corralling private investment for what it calls “America’s first-ever International Climate Finance Plan.”Almost immediately, congressional Republicans lined up against such a plan. “As far as global emissions are concerned, unless China stops its uninhibited growth of emissions, anything we do will be off-set fourfold by the Chinese,” said Garrett Graves, the ranking Republican member of the House Select Climate Committee.On the flip side, among environmental advocates, the dollar figures on offer from the White House fell far short. Joe Thwaites, an associate in the World Resources Institute's Sustainable Finance Center, said the new climate finance plan “starts to play catch up after the U.S. was largely absent for the last four years,” a period when many other countries raised their ambitions dramatically. “This is insufficient to address the needs described by vulnerable countries today, and nowhere near the balance with mitigation finance called for in the Paris Agreement.”3. America’s new emissions commitment got very mixed reviewsThe summit ended months of speculation, going back to the 2020 presidential campaign, over how Biden would bring the U.S. back into the international fold. The ultimate answer was a huge leap compared to the past four years of U.S. climate policy, but only a modest step on the scale of global action. The many climate groups to express disappointment included the activist collective Extinction Rebellion, which dumped wheelbarrows full of cow manure in front of the White House.A 50% cut below 2005 levels by the end of the decade may not even be compatible with the Paris Agreement, according to an analysis published by Climate Action Tracker. The independent research group said that “an emissions reduction target of 57% to 63% below 2005 levels by 2030 would be consistent with” preventing the worst consequences of climate change, opening up a potential gap with Biden’s signature goal.The central question ahead for the U.S. is whether Biden can muster the support necessary to reach his target. Kerry maintained that much of the plan would be achievable through executive order. Observers see plenty of reasons to remain skeptical. “Although numerous analyses have shown that it can be achieved if all of the announced and contemplated policies are successfully and perfectly implemented,” said Robert Stavins, director of the Harvard Project on Climate Agreements, “the question is whether it will be achieved.”Not everyone came away disappointed in the U.S. effort. Cherelle Blazer, senior director of international climate policy at the Sierra Club, said that the lack of major new commitments today didn’t worry her. “If raising ambition is what they wanted, then I think that's what they did.”Jake Schmidt, senior director of the Natural Resources Defense Council’s international climate program, bestowed the summit with measured praise. “I’d give it a solid B,” he said.Along with other announcements over the past six months, the summit did help narrow the 2030 emissions gap by around 12-14%, according to Climate Action Tracker. The biggest contributions have been from the biggest emitters, including China, the EU, and US, it said. But there remains a huge gap of 20 to 24 gigatonnes of CO2 equivalent to put the world on track to 1.5C, it said.``It’s clear the U.S. is back in the climate game, and, for the first time, is lining up to be a leader,” said Niklas Höhne, of NewClimate Institute, a CAT partner organization.For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2021 Bloomberg L.P.