Carbon dioxide or CO2 is a greenhouse gas because it has the capability to increase the overall temperature of the earth's surface which can lead to serious environmental consequences. There are some experiments that can show how CO2 can increase the temperature of the surroundings.
You can set two large transparent jars of the same volume. Each jar should have one thermometer inside to record the changes of temperatures. The first jar is the control where it will contain the air and the second one is the CO2 jar where you can put some CO2 gas. It would be better if you can borrow a pressure gauge to see if the pressure of two jars is the same. Seal both of the containers and let it stand there for 24 hours. Measure the temperatures of both jars from time to time.