Injection of CO 2 into the subsurface for geological storage has an effect on the temperature of the storage formation and the CO 2 itself. Numerical investigations are an essential tool in describing the relevant processes that determine such changes and the impact they may have on the migration and the storage mechanisms of CO 2 in the subsurface. This chapter focuses on the numerical simulation of such thermal effects and their consequences. Simulating the temperature changes in a storage site can be of interest for temperature-based monitoring. Determining whether or how such thermal effects change the transport of CO 2 in the formation is important for the success of a CO 2 storage effort. In particular, this chapter examines a leakage scenario and how temperature changes could affect the leakage flow. The second part of the chapter presents results of a complex reservoir-scale simulation. The target formation forms an anticlinal structure at a depth of about 570-900 m (1870-2953 ft). Strong temperature effects can be expected because of the possible tran Numerical simulation of temperature changes caused by CO2 injection in geological reservoirs. Available from: https://www.researchgate.net/publication/230838241_Numerical_simulation_of_temperature_changes_caused_by_CO2_injection_in_geological_reservoirs [accessed May 3, 2017].