My assumption is that human survival beyond the next century requires the complete (and probably permanent) cessation of economic growth. (Reduced population might make growth possible -- but that is speculation on the far future.) In the developed nations any social order replacing capitalism must make make this reduction in energy use and production of goods a major consideration. Is this view very widely shared among leftists, or on this list?
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If we're unable to replace our current, heavy carbon inputing infrastructure with one that adds little or nothing to the carbon cycle then I believe you're right, some level of curtailment (harsh or not so harsh depending upon who you ask) is essential.
If, on the other hand, we manage to pull several quite tricky rabbits out of several very slippery hats all bets are off: "growth", in whatever form, will continue until some other planet-wide crisis threatens - for example, an asteroid such as 99942 Apophis.
Tamed combustion has been an astoundingly successful technology and will be a hard act to follow.
So the thing to do is track developments in very low or zero carbon inputing methods of transportation, energy and manufacturing.
Gar Lipow's Grist Mill is a good place to start:
If low or no emissions methods are robust enough to replace current techniques and if these low or no emissions methods are universally adopted (and you'll know we're deep into a new moment when you tune in the BBC on your HD vid and watch a beat up, fuel cell powered Toyota pickup speeding down a dusty trail in Afghanistan or some other big sky locale) then we just might dodge this bullet.
.d.