3) footprint reductions by implementing techniques that are already viable. Some are even age-old.
Some are available...
However, just like with anything else, there are countervailing economic interests as well.
For instance, we're all aware of the fossil fuel one, but phasing that one out globally would be tough.
It's going to be a very hard to get developing countries to give up fossil fuels, on account of many of them just getting their hands on that technology recently.
"
Hey, we realize that the rest of us have built massive wealthy societies of this technology, and you just got access to it 20 years ago...gee whiz, bad timing, we decided it's bad now (after we've already leveraged it for a century) so you're going to have to scrap it" is going to be a very tough sell for obvious reasons.
As would the factory farming of animals.
Point of reference, global livestock consumption would have to be reduced by 70% globally for it to cut emissions by 20%.
The trade-off on that? The livestock sector (globally) employs over a billion people.
For the techniques that are already available, I feel like if those were palatable to large swaths of the population, they'd already be doing those things, that's why I mentioned newer technologies.
An example of what I'm talking about.
They've tried the imitation meat route, the uptake hasn't been substantial enough -- while some of them are technically edible (and some people pretend it tastes the same -- it doesn't), they need to ramp up their efforts on the lab grown meat technology. (which is still real meat and will taste identical, but without the ecologically destructive process for procuring it)