>Climate change is a great example of a wicked problem: Quick, somebody tell me what the acceptable maximum amount of CO2 in the atmosphere should be, in parts-per-milion! Provide me with the answer to that question, and you win a pony!
We don't know. At some point 450ppm was considered acceptable, but at this point the maximum acceptable level may well be 350ppm (pre-industrial revolution it was around 275ppm).
Right now we're at around 390ppm, so whatever it ends up being we have to reduce emissions from their current levels on at least a per-capita basis if not overall.
"We don't know" is the answer he is looking for to his rhetorical question. It's a value judgement. The island nations that are losing land to rising oceans have a very different idea of what is acceptable to northern nations enjoying longer growing seasons and milder weather.
The point is that we don't know. And it'll take literally trillions of dollars of effort to change our CO2 output substantially, so it's a bit of a sticky situation.
We don't know. At some point 450ppm was considered acceptable, but at this point the maximum acceptable level may well be 350ppm (pre-industrial revolution it was around 275ppm).
Right now we're at around 390ppm, so whatever it ends up being we have to reduce emissions from their current levels on at least a per-capita basis if not overall.