"dirty energy instead of renewables?"
Wow. You really do seem to be completely stuck in this dichotomous thinking mode.
Did you completely miss what he said about de-growth?
World energy use is about 150,000 terawatt hours.
Of those, about 120,000 are from ff.
http://en.wikipedia.org/wiki/World_energy_consumptionReduce energy use to a fifth of current levels (higher in some places, less or not at all elsewhere), and you suddenly have a mostly non-GHG forming energy supply.
Would that involve suffering? Sure. Did we fight WWII successfully with no suffering? No. Why should we expect to take on this much more important and much more existentially threatening task with no suffering.
But a lot of suffering could be avoided with a bit of planning: forgive debts, shorten the work week, provide universal basic health coverage, banish usury, redistribute wealth and land...
So it could be planned.
But probably it won't be.
In any case, most would probably survive drastic reductions in net energy use--humans lived for millennia on a tiny % of the energy now consumed and with no ffs.
What few if any
would survive is the hothouse world we are rapidly creating for ourselves and our progeny, with wetbulb temperatures across much of the populated world above survival levels for ourselves and the plants and animals we depend on.