By now, everyone should know what global warming is or at least heard of it. It's a problem that is hard to solve by nature because pollution is a negative externality.

Externality is the spillover or side effect of an economic transaction that impact parties not directly involved in the transaction

When your neighbour decide to burn their trash, the smoke is the externality. If you tell your kids to never burn in the open, that's will generate positive externality as the society benefits from well behaved citizens.

Our world is so complex and well-connected that each of us generates negative externalities whether we like it or not. If you drive, you contribute to the congestion and air pollution. As I was typing this, power used by my computer, lights and fan might be produced by an air polluting coal power plant somewhere else.

I do not know the answer to reducing negative externalities. Instead I think we should focus on creating positive externalities. If the things we do can somehow benefit some parties somewhere else, I think and I hope eventually that will enough to out-weight the negative effects of our complicated lifestyle.