[edit]
I do accept that it could become a whole-earth disaster that affects everything, but my point is that this may take generations.
No. I have that attitude, and I'm not dismissing either!
I think they're both serious problems that will cause a lot of pain as they're being worked through.
What I disagree with is doomsday scenarios where they'll be the end of human civilization.
I don’t know anyone that’s concerned about end of human civilization. What they are concerned about is the end of their lifestyle, part of which is due to relative world peace, which is in turn due to resources being somewhat available, at least to those with power.
Once those resources stop being so (cheaply) available, then you’ll see conflicts start emerging again. I already see it in my country, the US, with the widening gaps in places with economic opportunity and those left behind.
Add in water, electricity, changing weather patterns and there will be some pain in the future.
The problem I have with this argument is that "the end of human civilization" is such a high bar that it's practically a tautology that it won't be met.
WW2 didn't end the human civilization - it didn't even make a dent. In fact, if the Axis had won the war, conquered the rest of the world, and massacred everybody between Moscow and Shanghai, the human civilization still wouldn't have ended.
So any talk about whether the civilization will end or not, ultimately doesn't mean much.