So why now? Would it have been better to stop growing in Roman or medial times, for example? Or stop only in a 100 years? Degrowth seems to me like a vision of the future that assumes that humans should remain slaves of their environment and not become masters of it. If humans are to become the dominant species in the universe, degrowth will not help.
This is precisely where we were when people first started raising alarm bells about greenhouse gases.
The thermal emissivity of the night side of earth is only one of many limits we are running head first into. Almost all scarce resources, many abundant ones, and even abstract concepts like the growth of classical computation are all hitting limits where they only scale linearly or worse with energy input.
Growing into the solar system is largely irrelevant because it's a constant increase vs an exponential and will not be meaningfully coupled to earth's economy without energy expendature on earth proportional to trade volume. And there's no compelling reason to hinge everything on the assumption that the second law of thermodynamics and speed of light are both false so nothing outside the solar system is relevant to those living inside it unless we overturn one or both first.
All of this to avoid reexamining the blind faith assumption that we have to give an exponentially growing share of the pie to those who have the biggest share. Growth is only necessary for survival of the 99.99% if every year they give 2% of their wealth to the 0.01%