The former secretary of state took part in the virtual opening session of the first ever United Nations Climate Adaptation Summit (CAS) on Monday, which is being hosted by the Netherlands.
Mr Kerry said: “Three years ago scientists gave us a stark warning. They said we have 12 years within which to avoid the worst consequences of climate change. Now we have nine years left and I regret that my country has been absent for three of those years.”
He added: “We are proud to be back. We come back, I want you to know, with humility for the absence of the last four years and we’ll do everything in our power to make up for it.”
The high-level talks are aimed at setting out practical ways to protect communities in the coming decade from the impacts of climate change already taking place.
Mr Kerry highlighted that the US had spent $265bn in one year just to clean up after three storms. “We’ve reached the point where it is an absolute fact that it’s cheaper to invest in preventing damage, or minimising it at least, than cleaning up.”
He noted the critical goal of the Paris Agreement to limit global heating to 1.5C, and how the world is currently far off track, heading for a 3.7-4.5C future with current emissions.
This would mean “fundamentally unliveable conditions" for the most vulnerable and poorest people on earth, Mr Kerry said, and that it was a matter of “conscience and common sense” to urgently reduce emissions.
The climate envoy noted that President Biden was making climate change a “top priority”.
“We have a president now, thank god, that leads, tells the truth, and is seized by this issue. And President Biden knows we have to mobilise in unprecedented ways to meet a challenge that is fast accelerating,” he said.
He pointed to President Biden’s executive order to immediately rejoin the Paris Agreement on his first day in office adding that the US was committed to doing “everything we possibly can” to ensure the UN climate summit, COP26, “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.”
Mr Kerry’s comment appeared to hint that the US’s renewed efforts would need to be matched by countries including China, Brazil, Australia, and Russia in tackling emissions.
He said that work was underway on a new US Nationally Determined Contribution (NDC) - a target for reducing emissions - and that it would be announced as soon as “practicable”.
“The administration also intends to make significant investments in climate action both domestically and as part of our efforts to build back better from Covid," Mr Kerry said. "Internationally we intend to make good on our climate finance pledge.”
As part of the Paris Agreement, former president Obama pledged $3bn toward the Green Climate Fund to help poorer countries adapt. Mr Trump moved to withhold $2bn when he became president. In 2019, 27 countries announced contributions totalling $9.8bn. The US refused to contribute.
Mr Kerry closed his remarks by emphasising the importance of adaptation, and getting to net-zero emissions by 2050.
“There is simply no adapting to a three or four degree world except for the very richest and most privileged," he said.
“If we don’t act boldly and immediately by building resilience to climate change, we are likely going to see dramatic reversals in economic development for everybody.”
Even the most ambitious emissions reduction targets will no longer prevent severe climate impacts, and ramping up efforts to adapt are necessary.
The climate crisis could reduce global food production by up to 30 per cent, while rising sea levels and greater storms could force hundreds of millions in coastal cities out of their homes, summit organiser the Global Center on Adaptation (GCA) said.
"There is no vaccine for climate change," GCA chair and former UN Secretary-General Ban Ki-moon said on Sunday.
"It is happening much, much faster than we think, causing cascading risks and impact. Building resilience to climate change is not nice to have, it is a must have."
At the opening session on Monday, Ban Ki-moon praised President Biden’s decision to immediately rejoin the Paris Agreement on his first day in office.
The summit will not produce binding commitments but leaders will try to come up with an agenda for action to make nations more resilient.