Over the next two weeks, nearly 200 countries participating in United Nations climate talks in Azerbaijan will negotiate a new, possibly multi-trillion-dollar annual finance goal to help the world's poorest economies decarbonise and adapt to rising temperatures. But even though nations are doing the talking, much of the money isn't going to be coming from governments.

Developed countries, feeling cash-strapped these days, are already telegraphing at the start of the COP29 summit that a large part of any finance promised through these negotiations will need to come from sources out of their direct control. That includes the private sector through loans and other "innovative" finance structures.

The complicated and costly proposal to deploy more private finance is already being opposed by highly indebted developing nations, which are pushing for a narrower goal that places emphasis on delivering publicly financed grants. The strategy also raises a fundamental question: How can nations commit third parties, which aren't a part of the UN process, to mobilise hundreds of billions of dollars? The answer will be crucial in determining the credibility of any new pledge made in Baku this year.

In the diplomatic jargon of COP29, the main focus for the summit is to agree on a New Collective Quantified Goal on climate finance, which will replace a previous goal that promised $100-billion per year from rich nations to the developing world by 2020. Already there is distrust in the process. Developed countries came through two years late on their initial commitment, and some dispute whether the...