Abstract: Climate change has been described by the Lancet in a 2009 report as the biggest global health threat of the 21st century. Various impacts, such as vector geographic growth, sea level rise, wildfire risk, flooding risk, food security risk, and mental health impacts are all occurring or can be anticipated. Physicians can play a unique and important role in communicating on climate health impacts and advocating for more aggressive policies to mitigate CO2 emissions. Indeed, editorials in both the BMJ and CMAJ state that is essential that physicians engage on the topic. Canadian physicians have been powerful advocates for the Alberta coal phase out campaign, active transportation and bike lanes in Montreal, and other important campaigns. Suggestions for action both at an individual and collective level will be presented.