Objective: To investigate whether climate change has impacted on the nature of the obsessions or compulsions experienced by patients with obsessive compulsive disorder (OCD). Methods: The sample comprised 50 patients with OCD checking subtype who had presented at the Anxiety Disorders Clinic at The University of Sydney seeking treatment during the period March 2008 to November 2009. Details of the type of obsessions and compulsions directly related to climate change phenomena were identified. Results: Fourteen of the 50 participants (28%) were identified as having OCD concerns directly related to climate change. The most frequent concerns involved electricity, water and gas wastage. Less frequent concerns included pets dying of thirst and one participant was concerned about house damage due to floors cracking, pipes leaking; roof problems and white ant activity. Compulsions included checking and rechecking pet water bowls, light switches, taps, stoves, skirting boards, pipes, roofs and wooden structures. While these behaviours are not particularly unusual for people with this condition, it was the rationale they provided for carrying them out that was surprising. Instead of checking and rechecking so as to prevent fire or flood, the rituals were specifically performed so as to reduce their global footprint, or respond to climate change-induced negative events. Conclusions: Our findings demonstrate that the types of obsessions and compulsions experienced by 28% of our sample were directly aligned with the current issue of climate change and the perceived dangers associated with this phenomenon. To our knowledge this represents the first documentation of the significant impact of climate change on the nature of the concerns experienced by people with OCD checking subtype. We suggest that mental health professionals need to be aware of, and assess for the presence of such concerns.