Joe Biden has called upon the world to confront the climate crisis and “overcome the existential crisis of our time”, as he unveiled an ambitious new pledge to slash US planet-heating emissions in half by the end of the decade. Addressing a virtual gathering of more than 40 world leaders in an Earth Day climate summit on Thursday, Biden warned that “time is short” to address dangerous global heating and urged other countries to do more. Shortly before the start of the summit, the White House said the US will aim to reduce its greenhouse gas emissions by between 50% and 52% by 2030, based on 2005 levels. Biden said the new US goal will set it on the path to net zero emissions by 2050 and that other countries now needed to also raise their ambition. “Particularly those of us that represent the world’s largest economies, we have to step up,” the US president said in a speech opening the gathering. “Let’s run that race, win a more sustainable future than we have now, overcome the existential crisis of our time.” Biden said a shift to clean energy will create “millions of good paying union jobs” and that countries that act on the climate crisis will “reap the economic benefits of the clean energy boom that’s coming”. He said: “This is a moral imperative, an economic imperative, a moment of peril, but also a moment of extraordinary possibilities. Time is short but I believe we can do this and I believe we will do this.” The Biden administration has also outlined a new plan to double the amount of funding the US gives to developing countries struggling to adapt to the ravages of drought, flooding and other climate impacts. Other wealthy countries and the private sector should shift financing away from fossil fuels towards clean energy, Biden said. “This moment demands urgency – good ideas and good intentions aren’t good enough,” the president said. “We need to ensure the financing is there, public and private, to meet the moment on climate change and help us seize the opportunity for good jobs, strong economies and a more secure world.” A procession of world leaders then followed Biden, with Xi Jinping, president of China, urging countries to be “committed to harmony between man and nature” and stating that China will peak its emissions more quickly than other major economies. Boris Johnson, the British prime minister, stressed the importance of financial aid for countries most vulnerable to the climate crisis and said that cutting emissions wasn’t just an “expensive politically correct green act of bunny hugging”. Substantive new announcements came from Japan, with the prime minister, Yoshihide Suga, revealing it will slash emissions 46% by 2030, based on 2013 levels, an increase on its previous commitment. South Korea, meanwhile, committed to not financing any more overseas coal projects. Canada also upped its goal, to a 40% to 45% reduction in emissions by 2030, based on 2005 levels. The new US target, to be formally submitted to the UN, represents a stark break from the climate denialist presidency of Donald Trump and will “unmistakably communicate that the United States is back”, according to a White House official who was briefed on the emissions goal. “The US isn’t going to wait. The costs of delay are too great and our nation is resolved to act right now,” the administration official added. The US is scrambling to regain international credibility after Trump pulled the country out of the Paris climate agreement. But the Biden administration said it has already helped secure improved emissions reductions from Canada, Argentina and Japan, meaning that, along with new pledges by countries such as the UK, governments that oversee half of the global economy have targets consistent with stopping the planet’s average temperature from rising above 1.5C, a key Paris goal to avoid disastrous climate impacts. China, the world’s largest carbon polluter, has expressed some skepticism over the US’ return to the climate fold, but the White House is confident America retains its clout. “This new target gives us significant leverage to push for climate action abroad,” said the White House official. “Every ton of reductions achieved in the United States has multiplier effect in inspiring climate action overseas.” Faced with the task of coming up with an ambitious but feasible goal, the new US target does not match that of the UK and the EU but is still among the strongest pledges to date. António Guterres, the secretary general of the UN, said that a 50% reduction by the US was needed to help stop the planet slipping into a climate “abyss”, with scientists warning the world must slash emissions in half by 2030 if it is to curb calamitous heatwaves, wildfires, floods and societal unrest. “This is a groundbreaking step for our country,” said Al Gore, the former US vice-president. The Biden administration has reiterated it wants the US electricity grid to run 100% on clean sources such as solar and wind by 2035 in order to meet its goals and has framed an explosion in renewable energy and electric car production as a boon to American jobs. It has shied away, however, from mandating all vehicles sold by 2035 be zero emission models, despite a letter from the governors of a dozen states, including California and New York, urging the US president to do so. “It is very ambitious, even if one considers that US greenhouse gas emissions have actually been declining already since 2007,” said Flavio Lehner, a climate scientist at Cornell University, of the new US target. “Is this new pledge enough? Probably not, but this also depends on what other major emitters will do this decade.” The summit will feature a parade of leaders including the German chancellor, Angela Merkel, Vladimir Putin, the Russian president, Narendra Modi, the prime minister of India, and Scott Morrison, the prime minister of Australia. The gathering will be focused on themes such as clean energy innovation and the importance of oceans and forests, with speakers including Pope Francis and Bill Gates, the Microsoft co-founder. A constellation of other names surround the event, with Greta Thunberg, the Swedish climate activist, telling a US congressional committee that ongoing subsidies for fossil fuels are a “disgrace” while the Dalai Lama, along with 100 other Nobel prize winners, is calling for a phase out of fossil fuels. The summit will be just the first in a series of gatherings, including the G7 and G20, that will take place ahead of crucial UN climate talks in Scotland later this year. John Kerry, Biden’s climate envoy, said he hoped 2021 will see countries embrace a shift to clean energy in a transformation that rivals the space age or Industrial Revolution. “This is the greatest moment of transformation of our economy in our lifetime,” Kerry told the Washington Post. “We need to seize it.” Some climate activists have said Biden needs to do even more, however. “While many will applaud the president’s commitment to cut US emissions by at least half by 2030, we have a responsibility to tell the truth – it is nowhere near enough,” said Evan Weber, the political director and co-founder of the Sunrise Movement climate group. Kerry acknowledged that more needs to be done, claiming that the new US emissions target was a way of building back American credibility that was “destroyed” under Trump. “Is it enough? No,” Kerry said in a White House press conference on Thursday. “But it’s the best we can do today and prove we can begin to move.”