That we might owe nothing is a reasonable enough answer. But start by agreeing with the set up here from the IPPR:

The UK contribution to the UN’s climate fund should balloon to £20bn by 2030 if it plans to pay a “fair share” to helping tackle the global climate crisis, according to new research.

A report from the IPPR thinktank says the UK should “shoulder more of the burden” of the global climate crisis because of its major contribution to the world’s rising carbon emissions.

The left-leaning thinktank found that the UK is responsible for the fifth largest contribution of carbon emissions in the atmosphere since the 1750s. The UK is behind only the US, China, Russia and Germany in terms of its global climate impact.

The IPPR called on the next government to radically increase the money it spends on helping to fund green initiatives by almost threefold to match its contribution to the climate crisis with funds to help tackle the environmental breakdown.

Do we owe £20 billion a year?

Think on what the actual climate change solution is - assuming that we still agree with the IPPR just for the sake of the argument. It will be having a method of powering an industrial civilisation without the use of fossil fuels. And what is it that we in the UK have been doing this past couple of decades? We have been driving ourselves into fuel penury by subsidising research into and the scaling up of solar, wind, tidal and so on energy sources. We’ve already been giving that is, in the development of the required technologies. Rather than giving money other governments to splurge upon the problem.

Or, as we might put it, yes, we see that begging bowl but thanks, we already gave at the office.