That's a good point. I've also been wondering about how this differs between cultures (which has to be taken into consideration when designing interventions), specially after reading The WEIRDest People in the World by Joseph Henrich. A quote from the book:

The notion that market integration is associated with greater fairness or cooperation is jarring to many WEIRD people. Aren’t people from small-scale societies and rural villages highly prosocial, cooperative, and generous? Don’t markets make people self-centered, individualistic, calculating, and competitive? Yes, to both questions. To illuminate this seeming contradiction, we must distinguish interpersonal prosociality from impersonal prosociality. The kindness and generosity found in many small-scale societies and rural villages where I’ve lived and worked are rooted in intensive kin-based institutions that focus on nurturing and sustaining enduring webs of interpersonal relationships. It’s both impressive and beautiful, but this interpersonal prosociality is about relationship-specific kindness, warmth, reciprocity, and—sometimes—unconditional generosity as well as authority and deference. It’s focused on the in-group members and their networks. If you’re in the group or the network, it can feel like a long and comforting hug. By contrast, economic experiments typically tap market norms that prescribe fair dealing and honesty with strangers or anonymous others, especially in monetary transactions. This impersonal prosociality is about fairness principles, impartiality, honesty, and conditional cooperation in situations and contexts where interpersonal connections and in-group membership are deemed unnecessary or even irrelevant. In worlds dominated by impersonal contexts, people depend on anonymous markets, insurance, courts, and other impersonal institutions instead of large relational networks and personal ties."

He also gives many examples of the "impersonal prosociality" (i.e., trust, fairness, honesty, and cooperation with anonymous others, strangers, and impersonal institutions such as the government) that we have in WEIRD societies vs. non-WEIRD societies, such as:

• e.g., UN diplomats were allowed to park without paying for the ticket → diplomats from non-WEIRD societies did it much more
• Non-WEIRDS give less for the common good: e.g., blood; economics game where if everyone donates money to the common cash, everyone benefits more
• e.g., ultimatum game with a single run with an anonymous stranger (you have to offer some of the $100 you get, and if the receiver rejects it, nobody gets it) → WEIRD: almost everyone offers 50% (if less, they feel guilty); non-WEIRD: offer 5-25% (it already feels very generous, and don’t get why someone would reject free money)

Thank you for your points and questions. 
1. I focus only on anthropogenic GHG simply because despite feedback loops being also very important, it'd be too much off-topic. 
2. That'd be great!
3-6. Unfortunately, I don't know enough about the topics to say anything valuable, but interesting points. 

I agree that more GDP in rich countries may lead to improvements in many areas. However, I think that 1) we can't afford it given the problems of climate change, the rest of planetary boundaries, and resource scarcity; and 2) we may be able to improve in many areas without further growth, by investing on those areas which matter and shrinking destructive industries. Due to 1), we may need to compromise. If 1) isn't true, then great, let's continue the improvements!
Thanks for the link to your utopia project, looks really interesting!

1. I didn't actually mean that the urgency in the climate problem leads to urgency in the materials problem, both are urgent relatively independently. It seems you're more optimistic about material scarcity and that by the time we run into troubles, we'll already have tech to solve them. Would be great if that were the case. I'd love to see forecasts on that if you know some. 
2. The point I tried to make is that global warming is not the only problem. If it were, I wouldn't name it post-growth/degrowth, but I use these terms because of the bigger picture, since I also consider crossing the rest of planetary boundaries as well as resource scarcity important problems. But from #1, I think we disagree at least regarding the potential problem of resource scarcity. 

Thanks, didn't know that. 

Yeah, recessions tend harm SWB, but I don't see why a planned degrowth as I picture it would: e.g., if people work less, they'd earn less, but if we have UBI and more welfare, we may end up having more in the end. 
Reg #3&4: decreasing working hours would be costly (e.g., retraining). But if we're to consume less, we'd produce less, so there'd be less jobs available, so we can redistribute working hours. In reference to #1, it should ofc not be made in an authoritarian way, but I think there should be other ways, and less working hours should be related to more job satisfaction/more SWB.

I'm not sure I'm following your criticism against framing the question in terms of GDP, since my point is that we shouldn't really care about whether it grows or shrinks, and it seems that you agree (when you mentioned the carbon cap). 

Alright, so we agree we need to reduce GHG emissions, but when I say that we need to "shrink material throughput" it's not a conclusion, it's a separate point. To reduce GHG emissions it might even be better to grow our economy, but I think shrinking resource use and caring for the planetary boundaries are also important, and I'm more skeptical that this can be done under further economic growth. 

You may be right. I admit I lack the knowledge to answer that and I also see some potential problems for the global poor (in the post itself I already mention unemployment), about which ofc I care but I wonder whether they would be easily solvable or if they could be so big that it makes degrowth in rich countries unethical.