Am I correct?

Which of the following is an example of human impact on climate changes?
• the greenhouse effect
• changes in solar output
• global warming
• changes in the tilt of Earth's axis

2 answers

I'm not positive how to answer this.
Certainly b and d are not driven by humans and can be eliminated. Global warming, c, is attributed to human impact so that's a definite yes. A is the one I'm unsure about. The greenhouse effect is the name we have given to gases that cause an increase in earth's air temperature. Since it is a name that describes what is happening I don't think I would choose this as a human impact. Certainly man contributes CO2 emissions due to coal, automobile emissions, etc. and that is a human impact kind of thing but I'm inclined to think that the name itself is not. I think humans don't CAUSE the greenhouse effect since the greenhouse effect is caused by the nature of the chemicals causing that effect.
Sorry, I forgot to mark the one I think is the answer -- globa warming -- Thank you for your response. I am not a global warming fan so I wanted to be sure I answered the way they wanted me to.