Here’s a simple parable for climate change:
A large group of kids has congregated out on the sidewalk in front of their school. It started with just a few friends, showing off their latest video game. But the crowd grew, and now completely blocks the sidewalk. A guy in a wheelchair wants to pass, but can’t. The kids are so wrapped up in their own interests that they don’t even notice that together they have completely blocked the sidewalk.
Further along the street there is a busy pub. The lunchtime crowd has spilled out on to the sidewalk, and now has become so big that again the sidewalk is blocked. When the guy in the wheelchair wants to pass, quite a few people in the crowd recognize the problem, and they try to squeeze out of the way. But individually, none of them can make much difference to the blockage – there are just too many people there. They shrug their shoulders and apologise to the guy in the wheelchair.
In both cases, the blockages are not caused by individuals, and cannot be solved by individuals. The blockage is an emergent property of the crowd of people as a whole, and only occurs when the crowd grows to a certain size. In the first case, the members of the crowd remain blissfully unaware of the problem. In the second case, many people do recognise the problem, but cannot, on their own, do much about it. It would take concerted, systematic action by everyone in the crowd to clear a suitable passage. Understanding the problem and wanting to do something about it is not sufficient to solve it - the entire crowd has to take coordinated action.
And if some members of the crowd are more like the kids, unable to recognise the problem, no solution is possible.