The reason it matters whether it's caused by humans is: mitigation. If global warming is significantly affected by our release of massive amounts of CO2, we cou

The reason it matters whether it's caused by humans is: mitigation. If global warming is significantly affected by our release of massive amounts of CO2, we could theoretically help mitigate the issue by stopping, and possibly reverse it. If on the other hand the rise of CO2 levels is not a significant factor, then there goes our primary idea to solving the issue.