Developing countries may need as much as $US250-$US500 billion ($A270-$A540 billion) per year by mid-century to deal with the fallout from climate change, a UN report has warned.
The projected amount was as much as five times higher than previous estimates and significantly more than today's spending on climate adaptation, said the United Nations Environmental Programme (UNEP), which warned of a "significant funding gap after 2020".
"The impacts of climate change are already beginning to be factored into the budgets of national and local authorities," UNEP executive director Achim Steiner said in a statement on Friday.
"The escalating cost implications on communities, cities, business, taxpayers and national budgets merit closer attention as they translate into real economic consequences," he added.
In 2012-13, the amount of global public finance committed to adaptation was about $US23-26 billion, said the report, of which 90 per cent went to developing countries.
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Adaptation support is a key sticking point at UN negotiations under way in Lima to hammer out the broad outlines of a new world pact to curb global warming.
Poor countries most vulnerable to climate change-induced impacts - extreme weather events, floods, droughts and sea-level rise - are demanding that a rich nation commitment to adaptation and finance help be written into the pact.
But many developed countries insist that the deal, due to be signed in Paris in December 2015 to enter into force by 2020, should focus on mitigation - meaning efforts to curb planet-warming greenhouse gas emissions.
