It's all bacause of humans, and the main pollution is the factories, coal factories.
But there are lots more, like:
1- Cars
2- Houses
3- Too much carbon is going into the air
The efffects:Global warming meaning- The planet is warming every minute, by all the pollution like carbon which doesn't let half of the sunlight out to space, so it stays on the planet, warming the planet, which cause floods, acid rain, Warmer climates.Soon it will be 30- 60 Co
The bad thing is we can't stop it, but we can slow it down by reducing the amount of coal we burn and the big amount pollution we let out in the air