Billions were pledged to help poor nations adapt to global warming but trust is eroding as countries such as the US fail to put up the cash

The US and other countries need to pay up their $5.8bn of outstanding pledges to help developing countries to cope with climate change or risk derailing already fragile climate talks, the head of the UN’s Green Climate Fund has said.

Dozens of NGOs, governments and development agencies were queuing up to put to work a total $10.2bn in promised finance, said GCF executive director Hela Cheikhrouhou. Already 20 organisations have passed through the fund’s accreditation process, meaning they will be able to pitch for funding for projects, such as transitions to solar energy or drought-resistant crops that would help the developing world adapt to climate change or reduce emissions. She said she expected the number of accredited organisations to hit 100 and for the first tranche of projects to be funded before the Paris climate talks in December.

Cheikhrouhou said leaving 43% of pledges unfulfilled would damage developing countries’ trust that the rich world is serious about helping them adjust to the changing climate.

Rajendra Singh: Clean flowing rivers must be a human right Read more

“It certainly would erode the confidence because climate finance is one of the most difficult negotiation themes,” she said. “We need a stronger push from a high level.”

The GCF is often considered the sole shining light from the dismal climate conference in Copenhagen in 2009. It was set up as the main mechanism to raise $100bn a year in climate finance from rich countries by 2020 to assist poor nations that contributed little to global emissions to move to greener economies and build resilience to the effects of climate change. The fund would not run the projects itself, but accredit NGOs, development banks and the governments of developing nations to receive the money.

However governments have been reluctant to contribute money into the fund. During the lead-up to last year’s climate talks in Lima $10.2bn was eventually pledged, but even that is now proving difficult to secure. US president Barack Obama pledged $3bn, but it is unclear whether he will be able to pass the funding through a Republican congress France, Italy and Canada are also among the tardy.

The governments of Sweden and the Marshall Islands and the UN Development Programme (UNDP) joined Cheikhrouhou in urging those countries to fulfil financial promises they made before the Lima climate talks in 2014.

Nobody should underestimate how critical it is for the most vulnerable to know that the $100bn a year will be delivered Tony de Brum

Sweden is currently the largest per capita donor to the fund at $60.50 per person – six times more for each citizen than the US has pledged. The Swedish minister for international development cooperation, Isabella Lövin, said: “I hope that the US will also live up to its commitments because the US and the entire world will be affected by climate change.”

Marshall Islands foreign minister Tony de Brum said: “No issue is more central to trust in Paris than finance. Nobody should underestimate how critical it is for the most vulnerable to know that the $100bn a year by 2020 promised at the 11th hour in Copenhagen will be delivered. And right now, we have no understanding or assurance that even a fraction of that will be delivered. This is a big, gaping trust gap that needs to be filled before Paris.”

“The fact that the United States – which originally put the $100bn target on the table – is yet to make its own initial contribution to the GCF is a cause for concern. We all know the difficulties President Obama faces, but hope the US will make good on its own $3bn promise as soon as the new fiscal year ticks over next month.”

Small islands need debt relief to pay for climate change Read more

Cheikhrouhou described a “creeping sense of disappointment” because instead of building momentum for the GCF after a flurry of pledges in the lead-up to last year’s Lima talks, impetus appeared to be drifting away.

“I’m disappointed that no more new contributors have come forward in 2015,” she said, adding that she felt the fund needed to reach $15bn by 2018 in order to remain on track for the 2020 target. “My worry is, when I see the text of the Paris Accord, and see that references to the future of the Green Climate Fund are dwindling and weakening over the months.”

Hague climate change verdict: 'Not just a legal process but a process of hope' Read more

Fulfilling the pledges is also critical for the impetus for the climate talks in Paris, said Saleemul Huq, the director of the International Centre for Climate Change and Development.

“The UN talks on climate change have a history of financing pledges from developed countries which then are either not delivered or fudged. This seems to be happening again with the green climate fund pledges of $100bn a year from 2020 onwards, with current pledges only an insignificant fraction of that figure,” he said.

A spokesman for the UNDP said it was important all countries converted their pledges as “vast amounts of capital” would eventually be needed to tackle climate change.

However, the fund has achieved the 50% level of financing it needs to begin actively lending and Astrid Manroth, head of sustainable investment Europe at Deutsche Asset & Wealth Management (another of the GCF’s accredited entities), said she thought the level of finance would increase once the fund began investing in projects. This is set to happen at the next board meeting of the fund in November.

Overpopulation, overconsumption – in pictures Read more

“If there’s no change to the current status it will of course impact speed and scale of implementation. On the other hand, for me the binding constraint is project development capacity and project preparation. We need to get that right, and then I am convinced that there will be sufficient financing,” she said.

Join our community of development professionals and humanitarians. Follow@GuardianGDP on Twitter, and have your say on issues around water in development using #H2Oideas.