> the costs of de-carbonising the economy

The costs are supposed to be about $94 T just in the US: See

https://cei.org/blog/how-much-will-green-new-deal-cost-your-...

But there is no good evidence at all that human sources of CO2 have any significant effect on the temperature or climate of the earth: There is no good evidence that more CO2 would increase temperatures or that less CO2 would lower temperatures.

For some solid details that drive a stake through the heart of the climate alarmist monster, see

https://news.ycombinator.com/item?id=21933963

Here we can save the "costs", the $94 T in the US.