Climate change represents one of the most urgent challenges of our time. While national policies and technological innovation are essential, behavioural change at the individual and collective level also plays a crucial role in reducing emissions. Yet, as the IPCC's Sixth As- sessment Report highlights, individual action alone is insufficient unless embedded within wider structural and cultural change (IPCC, 2022). Voluntary initiatives such as citizen cam- paigns can nevertheless contribute by raising awareness, encouraging experimentation with new practices, and potentially building social mandates that support systemic climate poli- cies. Understanding the effectiveness and limitations of such measures is therefore vital for ensuring they contribute meaningfully to the ecological transition.

This report evaluates the "Mon Défi Carbone" campaign, a pilot initiative launched in 2025 by Impact Hub Geneva in collaboration with the Canton and City of Geneva and 2050Today. The campaign sought to mobilise residents of Grand Genève towards more sus- tainable lifestyles through a carbon calculator, thematic newsletters, public events, and part- nerships with local organisations. Over 1,400 participants registered, exceeding the initial target. Engagement data metrics were mixed, however, as many participants expressed sup- port, yet some events and partnerships were unfruitful.

The findings suggest that while the campaign succeeded in awareness-raising and in fram- ing sustainable behaviours as socially desirable, its primarily informational approach limited deeper,