If you build more nuclear or renewable, that takes pressure off of the oil and gas markets. With cheaper oil and gas, it would start making sense to switch ship

If you build more nuclear or renewable, that takes pressure off of the oil and gas markets. With cheaper oil and gas, it would start making sense to switch shipping from bunker fuel (literally the dregs of the fuel process) to a fuel source that is a little less polluting. Coal is dying in the US - not because of government R&D or political efforts (perhaps in spite of them) - but because of the prevalence of cheap natural gas and industry's ability to adapt when presented with a price incentive. The whole point of cap and trade is that it's easier for some sectors to adapt than others, and it's easier to just have them sort it out amongst themselves.