> Inside capitalism, we are faced with a choice between
>
> (a) immense misery for much of the working population
>
> or
>
> (b) unending growth which will destroy the environment.
>
> To preserve the environment growth must cease.
>
> But every single ("practical") proposal for dealing with the present
> crisis aims at the resumption of global growth.
Methinks your antinomy massively misunderestimates capital's ability push back its own limits. There no reason to believe that it can't make growth either environmentally neutral or even enhancing of the environment. Thinking it couldn't, it seems to me, is based on a pretty unhistorical view of capitalism. All it would require, as the elitist Deleuze & Guattari would say, is adding another axiom for the environment. The easiest way for capital to add axioms, of course, is with a push from the working class, and in this respect green capitalism would be capital's most brilliant innovation to date: it literally ties the continuation of life and the world with the continuation of capitalism, and it gets its antagonistic force to help it create this.
Your antinomy is a nonissue, as far as I can tell. Or rather, it's not an irresolvable impasse or unshakable contradiction. I'm tempted to say that the antinomy is a moral claim, a displacement or conflation of capital's conflict with labor onto the environment.