I am not sure about that. I believe that the survey you are citing is based on a limited sample to prove the author of your textbook's point. Also, factories are not the only problem: us breathing, volcanoes erupting, and cars driving also contribute to this problem. What are you talking about with the average temperatures being higher without the greenhouse effect? The greenhouse effect keeps warm heat in that "bounced off the earth." You are right in your point that too much CO2 is not the only problem contributing to global warming, but it does have a HUGE impact.
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