The US will hold a climate summit of the world’s major economies early next year, within 100 days of Joe Biden taking office, and seek to rejoin the Paris agreement on the first day of his presidency, in a boost to international climate action. Leaders from 75 countries met without the US in a virtual Climate Ambition Summit co-hosted by the UN, the UK and France at the weekend, marking the fifth anniversary of the Paris accord. The absence of the US underlined the need for more countries, including other major economies such as Brazil, Russia and Indonesia, to make fresh commitments on tackling the climate crisis. Biden said in a statement: “I’ll immediately start working with my counterparts around the world to do all that we possibly can, including by convening the leaders of major economies for a climate summit within my first 100 days in office … We’ll elevate the incredible work cities, states and businesses have been doing to help reduce emissions and build a cleaner future. We’ll listen to and engage closely with the activists, including young people, who have continued to sound the alarm and demand change from those in power.” He reiterated his pledge to put the US on a path to net zero carbon emissions by 2050, and said the move would be good for the US economy and workers. “We’ll do all of this knowing that we have before us an enormous economic opportunity to create jobs and prosperity at home and export clean American-made products around the world.” António Guterres, the UN secretary general, said: “It is a very important signal. We look forward to a very active US leadership in climate action from now on as US leadership is absolutely essential. The US is the largest economy in the world, it’s absolutely essential for our goals to be reached.” Donald Trump, whose withdrawal of the US from the Paris agreement took effect on the day after the US election in November, shunned the Climate Ambition Summit. Countries including Russia, Saudi Arabia and Mexico were excluded as they had failed to commit to climate targets in line with the Paris accord. Australia’s prime minister, Scott Morrison, had sought to join the summit but his commitments were judged inadequate, and an announcement from Brazil’s president, Jair Bolsonaro, of a net zero target just before the summit was derided as lacking credibility. The Climate Ambition Summit failed to produce a major breakthrough, but more than 70 countries gave further details of plans to reduce greenhouse gas emissions in line with the Paris agreement goal of limiting temperature rises to well below 2C above pre-industrial levels, with an aspirational 1.5C limit. Many observers had hoped India might set a net zero emissions target, but its prime minister, Narendra Modi, promised only to “exceed expectations” by the centenary of India’s independence in 2047. China gave some details to its plan to cause emissions to peak before the end of this decade but stopped short of agreeing to curb its planned expansion of coal-fired power. The UK pledged to stop funding fossil fuel development overseas, and the EU set out its plan to reduce emissions by 55% by 2030, compared with 1990 levels. Alok Sharma, the UK’s business secretary, who will preside over UN climate talks called Cop26 next year, said much more action was needed. “[People] will ask: have we done enough to put the world on track to limit warming to 1.5C and protect people and nature from the effects of climate change? We must be honest with ourselves – the answer to that is currently no,” he said. When Biden’s pledge to bring the US to net zero emissions by 2050 is included, countries accounting for more than two-thirds of global emissions are subject to net zero targets around mid-century, including the EU, the UK, Japan and South Korea. China has pledged to meet net zero by 2060, and a large number of smaller developing countries have also embraced the goal. The task for the next year, before the Cop26 conference in Glasgow next November, will be to encourage all the world’s remaining countries – including oil-dependent economies such as Russia and Saudi Arabia – to sign up to long-term net zero targets, and to ensure that all countries also have detailed plans for cutting emissions within the next decade. Those detailed national plans, called nationally determined contributions (NDCs), are the bedrock of the Paris agreement, setting out emissions curbs by 2030. Current NDCs, submitted in 2015, would lead to more than 3C of warming, so all countries must submit fresh plans in line with a long-term goal of net zero emissions. The US will be closely watched for its plans. Nathaniel Keohane, a senior vice-president at the Environmental Defense Fund, said: “The [Climate Ambition] Summit captured and reflected the momentum of recent months, but didn’t push much beyond it. The world is waiting for Biden to bring the US back into the Paris agreement, and will be looking for how ambitious the US is willing to be in its NDC.”