Sorry but it is irreversible.
Basically yes (theoretically no (think ultra long term..
)).
But your argument doesnt work, because it doesnt end at 3°C automatically, and - "we'll we then have to live with that". At a 6°C change in temperature, most of human civilization will have died out.
So rate of temperature growth matters.
Those (last paragraph) are usually the scenarios I lampoon as 'silly', because humans will take more drastic action to prevent those, but in your case I guess I even have to stress that.
I dont like to do that, because I hate motivating people politically with apocalyptic visions they will not encounter in the next 80 years - but its still a possibility just a bit further down the road. Growth isnt linear here either. So you dont have another 300+ years to get going either. (Thats what people in the risk assessment panel mean by 'the action windows for 1.5°C and 3°C max are small - we have to act now).)
And the later you act (starting to reduce impact, starting to reduce dependency on fossile fuels which will be running out eventually (factor of population growth and ressources being limited) the fewer options you'll have. Also the later you act, the more radical changes will become almost by default (more wars, less global trade, less wealth produced, maybe even insurance schemes simply faltering, because of risk that isnt projectable anymore, less prosperity, less time, ...).
The only thing you have to understand really is, that this is likely not a 'change' that you can innovate yourself out of with "technological advancement only". This is why 'driving people into reduced consumption' is a thing.
(Or you address it from the other direction and say - well, per capita GDP of western societies is projected to fall by 50% in the next 100 years, while the developing and second world is still growing. But that also can be argued for by "growing societies - cant be left to see their aspirations in living models, that your parents had", because limits of growth..
The only thing that can be argued really is, when you beginn the transitioning process. And how fast you are implementing it. (Or talk about population controlling schemes in a way that no one rather wants to.
The problem with those (at least those that dont involve armed conflict) is, that high population growth is connected to poverty. ("My children will care for me when I'm older, the state doesnt"), so reducing poverty is effectively reducing population growth as well (stabilizing population growth is something all 'advanced' societies have achieved. Otherwise, this always ends in conflict.).)
So if your goal is what the youth nowadays calls "global climate justice" - but which really means, reducing poverty, to reduce population, while also reducing average living standards in the west - thats actually the way to produce 'least harm' Sadly thats not how humans work though. (I can't extend my empathy that far, sadly).
(Societies in egypt existed for 3000 years without structurally changing systems really that much (sustainable). Ancient greeks changed that, introduced rapid (for the time) innovation, the notion that each generation should have it better than the last one - and its that model that arguably some people nowadays dont like anymore.
So curbed and managed human drives in terms of ambition and economic growth expectancy. Which means the same status quo for the next few hundred years.
Now there currently is the discussion if this can be rejiggered to some form of sustainable growth (virtual goods, societies of poets and thinkers, ...) (coined: decoupling growth from CO2 emissions), but the current consensus on that rather also is - no it cant. Certainly not at current levels.
(This is where designing peoples 'happyness' comes in (no joke
). So in the future - probably - you will be faced with more 'short term economic trends' that one can make a good living of, for maybe 10 years, and that then will go away again (no long term growth). Which is more like playing the lottery..
But it will distribute resources amongst - let say middle classes, not more 'justly' but more frequently.
Also there will be more (low paying) BS jobs, like the Microsoft Uplink platform featured in the video above (second one) impressively proves. (Just so that people won't rebel, you give them a 'higher societal goal' thats useless in regards of how we think about the economy today (wont ever get you the quiet house with garden at the edge of town (limited quantity of those arround... )) Hence Microsoft Uplink platform.))
And then you look at how "social mobility" looks like currently (in a world with negative growth - as we see it today) - and you start to laugh...
)
Now thats a basic, but more in depth look into this...
Also - part of the structural changes that seem necessary, maybe the generation that identifies so much with 'global climate justice' will be willing to 'take'. (This is a highly loaded (= explosive
) statement.)