A carbon footprint is a measure of the impact human activities have on the environment. What we do as humans in our day to day lives generates carbon (CO2) emissions. From the cars we drive to the energy we use in our homes, the spent fuel used to produce this energy releases carbon into the air. Without excess carbon in the atmosphere, the heat from the sun enters the atmosphere bounces off the earth and exits back into space. But too much carbon in the atmosphere keeps the heat from exiting and “traps” it like in a greenhouse (hence CO2 emissions are referred to as “greenhouse gases”). This is what causes global warming.