Has human activity caused the world's climate to change over the past 100 years?

Definitely yes. It is the modern human activity that has caused the desertification of green land for the sake of industrialization, and urbanization. One example is that the forests are consumed by the modern man for the newsprint in every corner of the globe.

The man has been exploiting the natural resources for the needs which are more than necessary, especially the fossil fuels, which has resulted in carbon and sulfur oxide emissions and even damaged the ozone layer that protects the earth's atmosphere.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.