How did global warming start?

I think that the world is becoming over populated, more factories are being built and our natural resources are running out because the factories are taking it away. The factories pollute the environment with carbon dioxide and green house gasses which destroys the ozone layer. The ozone layer is a shield around earth that block the ultra violet rays from the sun, when it's damaged it heats up the environment which causes Global Warming. China and India are the biggest polluters of all, both their countries have over 1 billion people and at least 50% drive cars which pollutes the environment. China produces most of the worlds products today, but how do you think they make it all, they use energy and gasses which ends up destroying the ozone layer. If the world stopped polluting so much we wouldn't be dealing with global warming and the world would be a better place.

Global Warming Effects