Greenhouse gas emissions, if left unchecked, can have disastrous consequences on the Earth. Professor Ram Ganeshan traces the carbon footprints of different entities and calls for a concerted response to reduce our impact on the planet. A “carbon footprint” of an entity – a country, city, event, firm, product or service − is the total amount of greenhouse gas emissions (GHG) it produces. Greenhouse gases other than carbon dioxide (CO2), such as methane, nitrous oxide, sulfur hexafluoride and others, are converted to their “CO2 equivalent” (CO2e) weight so that a single number can represent the environmental impact of the product. Since the 1750s, atmospheric concentrations of carbon dioxide have risen from about 280 to 379 parts per million (ppm). GHG emissions have led to a 0.6˚C increase in the global average surface temperature since 1900.