The United Nations Environment Program (UNEP) warned in a new report that spending on climate change abatement by wealthy nations was five to 10 times below the estimated needs.
"Climate change is landing blow after blow upon humanity, as we saw throughout 2022: most viscerally in the floods that put much of Pakistan under water," said Inger Andersen, Executive Director of UNEP.
"The world must urgently reduce greenhouse gas emissions to limit the impacts of climate change. But we must also urgently increase efforts to adapt to the impacts that are already here and those to come."
Many emerging economies least to blame for the fossil-fuel gases that stoke global warming, are also among the most exposed to climate impacts, such as worsening drought, floods and cyclones.
Funding to help them adapt to accelerating impacts and curb emissions is one of the thorniest issues at UN climate negotiations, which will begin their latest round in Egypt on Sunday.
Last week the UN warned the world was nowhere near the Paris Agreement target of capping warming at 1.5 degrees Celsius above pre-industrial levels.
In February, in a report dubbed an "atlas of human suffering", the UN's climate experts warned that global warming is outpacing our preparations for a climate-addled world.
The poorest are often the hardest hit and the least able to protect themselves.
"This is unacceptable," said UN chief Antonio Guterres.
"We need a global surge in adaptation investment to save millions of lives from climate carnage," he added, announcing a new tool to try to help fill this gap.
At the last UN climate talks in Glasgow, countries agreed to double their adaptation finance from 2019 levels by 2025, reaching $40 billion.
But even that target is under question after the increase from 2019 to 2020 was just four percent, the UN said.
"The reality is that the current model for delivering adaptation support quite frankly is broken," a senior UN official told AFP.