The world has until the end of the decade to halt the most catastrophic effects of climate change, the new US climate envoy warned on Monday. John Kerry, the former US secretary of state, told the Climate Adaptation Summit that the world's poorest countries face "unliveable conditions" by 2030 in a worst-case scenario. He acknowledged that America had been absent from the international effort to tackle climate change during Donald Trump’s presidency but said that the country “is proud to be back”. "Three years ago, scientists gave us a stark warning. They said we have 12 years to avoid the worst consequences of climate change," he told the Netherlands-hosted summit, which was held online. “We have nine years left, and I regret my country has been absent for three of those years.” Mr Kerry pointed to President Joe Biden’s executive order to rejoin the Paris Agreement on his first day in office as evidence that the US was committed to the fight. He said the US stood ready to tackle global warming in unprecedented ways and vowed to announce a new climate plan as soon as practicable. He did not give a timeframe on when new measures would be ready but marked increased climate funding, better co-operation with international bodies and making US climate data more widely available as priorities. Mr Kerry said that he hopes the upcoming Cop26 climate summit in the UK provides “results in ambitious climate action in which all major emitter countries raise ambitions significantly and in which we help protect those who are the most vulnerable”. He said that major population centres faced a “fast-accelerating” threat with limited time to act, and that only the wealthy could afford to adapt to a global average temperature rise of between 3.7°C and 4.5°C. “It invites for the most vulnerable and poorest people on earth fundamentally unliveable conditions,” he said. Meanwhile, UK Prime Minister Boris Johnson said that 2021 must be the year the world fights back against climate change. He announced the formation of the Adaptation Action Coalition in partnership with Egypt, Bangladesh, Malawi, the Netherlands, Saint Lucia and the UN. “We look to Bangladesh and see more powerful and more frequent storms and cyclones. We look to California, Australia and see soaring temperatures and raging wildfires. We look to the island nations of the Pacific and see whole communities submerged by rising seas,” he said. “We cannot deny that dramatic climate change is already happening, already devastating lives and economies.” The group "will work to turn international political commitments made through the UN Call for Action on Adaptation and Resilience into on-the-ground support for vulnerable communities”. Mr Johnson said he hopes the issue of climate change will help to boost Britain's relationship with the US under Mr Biden. French President Emmanuel Macron said a third of the country’s €6 billion ($7.2bn) will be earmarked for climate change resilience. He said the pandemic showed that populations “need to be protected from shock”. UN Secretary-General Antonio Guterres said that World Meteorological Organisation statistics show there have been 11,000 natural disasters in the last 50 years, costing the world more than $3.6 trillion. “Extreme weather and climate-related hazards have also killed more than 410,000 people in the past decade, the vast majority in low and lower middle-income countries,” he said. “That is why I have called for a breakthrough on adaptation and resilience. We need the trillions of taxpayers’ dollars funding the recovery from the Covid-19 pandemic to jump-start the low-carbon, high-resilience future we need.” International Monetary Fund managing director Kristalina Georgieva said the world needed “all hands on deck” and called on governments to direct more funds to climate resilience. “For us, it’s mission critical,” she said. The summit’s host nation, the Netherlands, has centuries of experience in adapting to the threat of water, from major rivers that run through the low-lying nation to its long North Sea coast. The country shares its know-how around the world, for example, to flood-prone Mozambique, where Dutch experts have helped strengthen drainage systems and coastal defences. The online event aims to set out practical solutions and plans for dealing with climate change in the period until 2030. Dutch Prime Minister Mark Rutte said the world faces a sharp drop in food production, a lack of water for drinking and more extreme weather events should it fail to limit climate change. He said adapting to climate change for low-lying nations, such as the Netherlands, was “a matter of pure survival”. “We are reaching the limits of what climate, nature and the environment can handle. Business as usual is no longer an option,” he said.