How does too much CO2 in the atmosphere effect the climate?

CO2 is a greenhouse gas. Too much CO2 in the atmosphere will make the climate hotter because it acts like a 'greenhouse' or blanket as it insulates heat in the atmosphere. CO2 allows heat to pass into the atmosphere but it doesn't allow heat to pass out into space. Too much CO2 in the atmosphere would trap the heat in the atmosphere, causing climate change.