What are the sound reasons (let's put aside the unsound reasons) why decarbonisation takes us further down the road to sustainability; and what real-world circumstances might mean that some specific decarbonisation measures make sustainability harder to achieve?
I'm using decarbonisation as shorthand for reducing the greenhouse gas emissions from electricity, heating, transport, industry, land use, land use changes and forestry. Where greenhouse gas emissions are taken to be those anthropogenic emissions that increase the net forcing effect - so not water vapour emissions, and not emissions of CO2 where the carbon was already part of the carbon cycle.