It’s quite possibly higher than it has been in millions of years, although I haven’t checked that… and it’s almost certainly only higher as a direct result of us pumping out the stuff…
And the people that are killed by the floods? It’d probably be hard for them to migrate if they were dead… and many of the lowland areas are also less developed, so they’ve probably caused a lot less global warming than the people in higher areas.
I don’t know about the amount of pollution produced by airplanes, so I can’t comment on that…
You could say that you exhaling is harming me, although you not exhaling is likely to hurt you more than I’m hurt by your exhaling 
But the point is that a car emits many, many more times the amount of CO2 than a person does.
