John answering your questions requires that I recite the research done, which shows why I've come to the conclusions reached. I've more or less given up trying to do this, because it's all published in Medium, well over 400 articles, and it's the fault of Medium being a for-profit platform, like all platforms, that you are shown articles by Mr Barnard, whilst never seeing any of mine, despite my background, my articles are buried by the system because they question the role of profit.
For-profit algos can't understand non, or even anti-profit information, so the latter is consigned to nonsense, or pseudo science, whatever, it's the physical truth that matters, but obviously not to the algos, since profit itself is an energy lie, an untruth, every time profit is practiced, the temperature is pushed up, just a little more.
Profit is exclusively energy extracted from the planet.
To get to the bottom of all this you need to audit all energy flows.
To do that, you need to mathematically sign energy according to the direction it flows in, positive from sun to Earth, negative where we take it back out and throw it to heat.
I have checked to see if Mr Barnard does that, and note he doesn't, so I would conclude he is actually unqualified to make any conclusions on things overall, though he might not be aware of that limitation, he can't possibly understand the complete system if he doesn't at least do that.
A little knowledge is dangerous, sometimes.
Anyhow the atmosphere is adiabatic by definition, just look at the definition of adiabatic, look at the atmosphere and ask whether or not the atmosphere is adiabatic, don't just take my word for it, check it out, think about it.
Either the atmosphere is adiabatic by definition, or there are greenhouse gases, they can't both be true, it's one or the other, and because I've had to use the concept of adiabatic in many practical scenarios to create actual working physical systems, my inclination is to go with adiabatic being true.
On "Renewables" other than solar, we have to sign them as mathematically negative, because they take things on the planet which were not heat, and convert at least part of that non-heat energy to heat, therefore the effect on heat, by them, is to increase it, and if you accept this heat is direct increase of entropy because there are no greenhouse gases, then this is adding to destruction, and of course it is fully compatible with profit, hence why we still do it, despite not having to do it because in theory we could easily expand solar to do all, but we don't, because the latter is incompatible with profit.
Monetising solar can only be done by issue of money for free. I can show physical numerical proof of that, done on actual utilities and population data.
What we are doing with non solar renewables is just the same as what we did with fossil fuels, we undo what nature created, things that would have been heat from the sun had nature not created them, and throw them back to heat.
The damage they do is obviously a lot less than fossil fuels, but look the damage being done, is not just down to fossil fuels, we've desertified as long as profit has existed.
Stopping fossil fuels alone can't stop the destruction, and we are more or less up against an immovable wall of how much more damage we can do (how much more profit can be made) before we do something that triggers abrupt massive trauma.
Its just more destruction.
Profit is monetised destruction.
On hydrogen, given we do monetise solar by solar indexed stimulus as needed to recover the energy value in money, by having it honestly refect the KWhrs coming in from the sun, this removes all concerns of hydrogen efficiency.
A kg of hydrogen created by solar is 33KWhrs removed from the energy of the sun on the planet, regardless of system efficiency.
Efficiency just changes how quickly this can be done but the end result is always the same, undeniably a cooling effect, rather than a heating effect.
Who cares about efficiency in that scenario, especially if money is for free also, why worry about the cost of adding more hardware to increase rate of hydrogen production?
We might worry about the energy needed to produce the hardware, but wait, can't that be fueled by hydrogen also, therefore becoming solar powered?
I think so. In fact, I'd say I know so.
And how else will we keep aerospace airborne, after fossil fuels are quit anyhow?
Rolls Royce have already flight tested aerospace engines on hydrogen and all looks good.
Just one challenge remaining there, it's the liquificatiion of hydrogen at room temperature, to move it away from causing embrittlment, towards storing in low pressure aerosol style tanks.
Apparently, according to the research carried out on this to date (None!), funded as always by fossil fueled interests, it isn't possible.
I would put my entire fortune, reputation, credibility, or whatever might still exist, on achieving that in very short order.
There is absolutely no evidence of it ever even being tried, it's just "Impossible" but nobody can explain why.