The United States is "proud to be back" in international efforts to tackle global warming, Washington's new special climate envoy John Kerry told a summit of world leaders on Monday.
US President Joe Biden is this week expected to release more policies to tackle climate change after rejoining the 2015 Paris climate agreement that predecessor Donald Trump quit saying it was too costly to the US economy.
"We're proud to be back. We come back with humility for the absence over the last four years and we will do everything in our power to make up for it," Kerry told the virtual Climate Adaptation Summit, hosted by the Netherlands, by video link.
Kerry was joined by China's Deputy Prime Minister Han Zheng, German Chancellor Angela Merkel, French President Emmanuel Macron, British Prime Minister Boris Johnson and others.
"President Biden has made fighting climate change a top priority of his administration. We have a president now, thank God, who leads, tells the truth and is seized by this issue," Kerry said.
Kerry, who signed the Paris agreement when he was US secretary of state, said Washington would "make good" on previous global climate finance commitments by investing in climate action domestically and abroad.
Under former President Barack Obama, the United States pledged $3 billion to the global Green Climate Fund to help vulnerable countries fight climate change but only delivered $1 billion.
Leaders at Monday's summit, which aims to help countries build resilience against climate change, stressed the importance of having Washington back at the table.
"To tackle this great challenge we need all hands on deck and certainly the US is so critical for success," said International Monetary Fund Managing Director Kristalina Georgieva.
U.N. Secretary-General Antonio Guterres said "the Covid-19 pandemic has reminded us that we cannot afford to ignore known risks. Climate disruption is a risk we are well aware of".
Climate change could depress global food production by up to 30%, while rising seas and greater storms could force hundreds of millions of people in coastal cities out of their homes, summit organiser the Global Center on Adaptation said.
Although droughts, fires, heatwaves, floods and other climate extremes related to global warming have intensified, investments to shield people from these risks have remained modest, scientists wrote to leaders taking part.
"Unless we step up and adapt now, the results will be increasing poverty, water shortages, agricultural losses and soaring levels of migration with an enormous toll on human life," the 3,000 scientists wrote.
Developing countries alone need to spend around $70 billion per year to battle the effects of global warming, a U.N. report showed this month, and those costs could jump to $140 billion to $300 billion by 2030.