If carbon dioxide (CO₂) were a politician, it would be worried about its bad press. The greenhouse gas is the primary pollutant responsible for climate change.  Not only are scientists, leaders, and activists trying to halt its production, but they also want to capture it directly from the air and lock it underground where it will do less harm.  

(Learn more about greenhouse gases, the chemicals warming the planet.)

This gas, however, also plays a key role in life on Earth.  

Carbon helps form the protein and DNA found in living things. In the atmosphere, it combines with two oxygen molecules to form carbon dioxide.  

Carbon dioxide is a