Is CO2 Polar or Nonpolar?

Answer: CO2 is a nonpolar molecule because the charges on either side of the molecule (180˚ apart) balance each other out. 

CO2 Ball and Stick Model
CO2 Ball and Stick Model. Created with Avagadro 1.2.

Although the bonds between carbon and oxygen are polar covalent (since the difference in electronegativity is greater than .5), the bonds cancel out the pull on carbons electrons due to the linear structure. Therefore there is no region of the electron that has either more positive or negative charge. If you are interested in learning more about the structure of CO2, feel free to check out this article on the lewis structure for CO2.

Why is CO2 so important?

Carbon Cycle
Carbon participates in many critical processes such as photosynthesis, thereby traveling the globe mainly through the carbon cycle. By providing a source of carbon to autotrophs (i.e. photosynthesizing organisms), CO2 allows them to continue building organic material critical to the survival of all other ecosystems.