In a recent forum post Grant suggested a new scenario for the collapse of civilization by the loss of the GPS system. Thinking of possible other new scenario's made me think of one that is currently very real and without a doubt will cause real world wide problems in the near future (next 100 years): pollution and climate change.
I'm not a tree hugger or green activist but I do realize that world pollution has become such a big problem that it's possibly already at the point where it can't be reversed without a certain level of collapse of the current civilization. This could be a scenario for stories that I haven't read before.
Some points I thought about:
It's a slow process. Not like the fast processes like a virus, meteorite strike, or EMP disaster.
Different sources disagree on the current number of deaths per year caused by pollution. The numbers vary between 6-9 million per year and 1 in every 6 deaths. Imagine what what the numbers will do when pollution keeps increasing the way it does and climate change causes more and more disasters. It's certain to cause huge problems.
Big business is increasing it's power base every year (Google, Amazon, etc.) and increasingly influences politics. They have a two-sided interest: the cost of clean production or cleaning up is just that, a cost. No real motive to spend money on it. On the other hand it kills people, the very source of their profits.
Since it's a long term process a lot of people, and specifically businesses, have a way of thinking like "I'm not around anymore when it gets too bad". Politics could do what needs to be done but since it will definitely harm business they don't act like they should do, "think about the elections!".
I imagine a story where we are ~50 years in the future and it has gone really bad. Maybe there's a big business that now sells clean air and clean water because it has to be processed before it's even breathable or drinkable. A large part of the population has already died, will soon die, is too ill too do anything, or too poor to buy clean air and water. Birth rates have dropped dramatically and many are born with defects. Climate change causes regular, huge natural disasters.
There will be a point where it all collapses. I can see different possibilities for good stories using this scenario. Collapse into chaos, slow decimation of the population without real chaos, or war because some countries keep polluting while others started huge efforts to clean up. There's also possibilities for stories that tell about the rebuilding with ~20% of the current population left, unlike most PA stories where very few are left to rebuild.