Actually, it kinda is the almighty issue of the day, similar to how nukes and the cold war was that issue for our parents and grandparents. It's a reflection of humanity's kryptonite, a problem that is both too big (to fix) and too slow/small (to care about), simultaneously. Somehow.

If we can't grow up enough to address it in a serious fashion, we're going to rip ourselves to shreds in the coming centuries, as technology gives us more and more power to change our world in ways we can't necessarily foresee. With nukes, we just had to "don't shoot", and everything would be fine. No apocalypse. With this, and other potential future problems, we have to do something to help, we can't just wait and do nothing this time. We need to devise a new general strategy, better than wait-and-see.

Regarding mass-transit, that's a more complicated issue. Global warming is not though, global warming is a very simple issue. Which ends up being part of the problem, annoyingly, as it's so easy for people to come to lazy conclusions concerning it.