Explanation:

According to the World Health Organization (WHO), a carbon footprint is a measure of the impact people’s activities have on the amount of carbon dioxide (CO2) produced through the burning of fossil fuels and is expressed as a weight of CO2 emissions produced in tonnes. 

• It is usually measured as tons of CO2 emitted per year, a number that can be supplemented by tons of CO2-equivalent gases, including methane, nitrous oxide, and other greenhouse gases.
• Carbon footprint is different from ecological footprint. While the carbon footprint measures the emission of gases that contribute to global warming, the ecological footprint focuses on measuring the use of bio-productive space.

Hence only statement 1st is correct.