The world's 48 poorest countries will need to find around a trillion dollars between 2020 and 2030 to achieve their plans to tackle climate change - and those plans should be a priority for international funding, researchers said.
Estimates based on plans submitted by the least-developed countries (LDCs) toward a new U.N. deal to curb global warming show they will cost some $93 billion a year from 2020, when an agreement expected to be ironed out in Paris over the next two weeks is due to take effect.
That includes $53.8 billion annually to reduce emissions and $39.9 billion to deal with more extreme weather and rising seas, according to a report from the London-based International Institute for Environment and Development (IIED).
IIED Director Andrew Norton said the least-developed countries currently get less than a third of all international climate funding provided by wealthy governments.
"A fair and effective deal at Paris should prioritise the investment of international public climate finance for this group to implement their climate action plans, while agreeing measures to help better-off countries attract private climate finance," he said in a statement.
The least-developed countries - from Ethiopia to Zambia, and Yemen and Pacific island nations - are home to some of the poorest communities who are suffering the worst impacts of intensifying droughts, floods, storms and crumbling coastlines.
Yet they produce just a tiny fraction of the planet-warming gases that drive climate change.
Such countries have a widespread lack of resources and expertise to tackle climate change. But all 48 have produced so-called Intended Nationally Determined Contributions (INDCs) to a new global climate deal.
These plans set out how they will curb their emissions from 2020 - by shifting to renewable power sources, such as solar, or building cleaner public transport, for example.
They also outline what countries need to do to help their people live better with climate change impacts. In some cases, they say how much all this action will cost.
The IIED report noted that three countries - Burkina Faso, Djibouti and Zambia â€” are showing "extraordinary commitment" by aiming to find more finance within their borders than beyond them.
"Even so, all LDCs agree that fulfilling their INDCs cannot be done without a significant contribution from international climate finance, whether it be public or private," it said.
The least-developed countries "cannot hope to implement their INDCs quickly enough alone", it added.
The countries will require technology sharing and help to build their capacity, as well as investment capital, particularly for high start-up costs. Much of the money must come from international sources, the report said.
ADAPTATION LOSES OUT
Despite poorer countries' clear need for funding to combat climate change, the lion's share of government finance goes to wealthier nations, it noted.
Brazil, China, India, Morocco, South Africa and Turkey are receiving as much public money as all the least-developed countries together, the report added.
And of the annual $11.8 billion in donor government money flowing to the least-developed countries in 2013 and 2014, the bulk - $10 billion - went to support efforts to curb emissions.
Just $1.8 billion was allocated for adapting to climate stresses, according to recent figures from the Organisation for Economic Co-operation and Development.
The Paris talks are due to clarify how rich countries will mobilise a promised $100 billion per year by 2020 to help poorer nations develop cleanly and withstand climate pressures, and set out a longer-term path for climate finance.
There is growing pressure from African and other developing countries for donors to give a larger share of their money for adaptation, which has received less than a fifth of the total.
"Making finance available is one thing, but ensuring it gets to those who need it most is another," said Norton.