I don't know what your first sentence means. A carbon tax puts into focus which carbon emissions are truly essential, and which ones are optional, expressed by the spending choices consumers make. If you have it in place and most voters agree with the principle (because they make money) then you move the tax rate slider up or down to get carbon emissions to whatever level is enough.
My first sentence means that UBI doesn't change anything to somehow make the offered definition of what kind of carbon pollution is destroying the world valid.
"Essential" doesn't mean anything to the physics of climate change, it just means something like "what people choose to do".
