Transport is a major source of human CO2 emissions. Focusing on individual mobility, this article attempts to capture the socioeconomic factors that explain the CO2 emissions resulting from mobility, as well as their developments in recent years. It is based on the last two national Transport surveys conducted in 1994 and 2008. These surveys provide a picture of all journeys made by people residing on French territory, whether these journeys are local, long-distance or abroad. For the purposes of the article the emissions from each journey collected by the surveys were estimated, allowing us to determine the explanatory factors and dynamics at work behind the aggregated results at a very detailed level. Emissions grew by 14 % between 1994 and 2008, but the trends in daily journeys are not the same as those in long-distance travel. The very sharp rise related to local journeys (+17%) was caused, most notably, by the growth of urban sprawl, while the inhabitants of central urban areas reduced their mobility and their emissions. The factors of this increase mainly reside in the commuting constraints of the active population, as well as in generational shifts such as the significant increase in the number of older workers and their greater tendency to use cars than the previous generation. In long-distance travel, the rise in the number of journeys recorded over the period is partly offset by a drop in unitary emissions, and the growth in CO2 emission (+8%) mainly reflects the growth in the population (+6%).