Canada is, as far as countries go, relatively cold and sparsely populated. Our houses are large by global standards, and we drive a fair amount. We are rich enough to consume a lot of stuff. These factors, together with the oil sands, mean that we have one of the world's highest levels of CO2 emissions on a per capita basis: 13.5 metric tons (MT) per person in 2013.
Over the past decade, Canada has been admitting about a quarter of a million new immigrants annually. The majority of them come from countries, such as the Philippines, India or China, which are warmer, poorer, and more densely populated than is Canada - and where the typical person produces far fewer CO2 emissions on a per capita basis. When someone moves from one of these countries to Canada, and adopts a Canadian lifestyle, their "carbon footprint" - the amount of carbon they use in their daily lives - would be expected to increase. This is the carbon cost of immigration.