Abstract. Cooking organic aerosol (COA) is one of the major constituents of particulate matter in urban areas. COA is oxidized by atmospheric oxidants such as ozone, changing its physical, chemical and toxicological properties. However, atmospheric chemical lifetimes of COA and its tracers such as oleic acid are typically longer than that have been estimated by laboratory studies. We tackled the issue by considering temperature. Namely, we hypothesize that increased viscosity of COA at ambient temperature accounts for its prolonged atmospheric chemical lifetimes in wintertime. Laboratory generated COA particles from cooking oil were exposed to ozone in an aerosol flow tube reactor for the temperature range of -20 °C ~ 35 °C. The pseudo-second order chemical reaction rate constants (k2) decreased by orders of magnitude for lower temperatures. The temperature dependence of k2 was fit well by considering diffusion-limited chemical reaction mechanism, suggesting that reduced viscosity was responsible for the decrease in chemical reactivity. In combination with the observed global surface temperature, the atmospheric chemical lifetimes of COA were estimated to be much longer in wintertime (>1 hour) than that in summertime (a few minutes) for temperate and boreal regions. Our present study demonstrates that the oxidation lifetimes of COA particles will need to be parameterized as a function of temperature in the future for estimating environmental impacts and fates of this category of particulate matter.