This paper presents a carbon footprint (CF) observatory recently developed within our research group. It aims to introduce a new concept of CF accountability, which focused not just on measuring CF, but also on making users reflect about and eventually change their lifestyles to reduce their personal emissions. With this conception, the CO2web observatory includes not only a CF calculator, but also the CF of different alternative consumption scenarios. Therefore, the user may be more aware of the impact of different personal decisions, such as emissions linked to different food, cars, home appliances or pets. In addition, the CF calculator provides quantitative comparisons of the emissions linked to current habits of users with those of similar cohorts, along with specific advices for those consumption sectors where emissions are significantly higher than their cohort’s average.