Why too much CO2 so Bad to Our Environtment?

Everyone probality know about the effect of CO2 Also we know as Carbon dioxyde. This gas was emitted by Cars, buses, plans, boats and etc. However, humans and animals also produce this gas naturally. As we inhale oxygen, we exhale CO2. Therefore, there is nothing wrong with the gas CO2 itself. The problem is that we have produced such a big amount of CO2 due to human actions, that the amount of CO2 we find in the atmosphere is dangerous.