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The temperature of deep hydrothermal sedimentary reservoirs varies between 50 and 250 degrees C, while the temperature of injected CO2 can be much below the reservoir temperature. Most past studies did not consider temperature effect on the CO2 dissolution trapping in storage reservoirs. We have performed numerical simulations of coupled multiphase flow, solute, and heat transport for liquid/supercritical CO2 injection in a storage reservoir for different reservoir temperature, injection temperature, and reservoir permeability. During the injection of relatively cool CO2 in a warmer storage reservoir, brine density increases with CO2 concentration causing solutal fingering in the diffusive boundary layer and the creation of an isolated dissolved CO2 plume (gravity trunk) below the injection zone. We have found that in many cases, the formation of a gravity trunk creates a large convection roll beneath the injection point. For low and moderate reservoir temperatures (100 and 175 degrees C), solutal fingers are pulled towards the injection zone by the large gravity trunk convection roll. In contrast, for higher temperature reservoirs (>206 degrees C), brine density decreases with dissolved CO2 concentration. Hence, for a reservoir temperature of 250 degrees C, solutal fingers do not develop, but reverse fingering from a dissolved CO2 mound is visible. We conclude that dissolution trapping achieves greater effectiveness for a reservoir temperature of 175 degrees C than those at 100 and 250 degrees C. We have also observed that free-phase CO2 below the caprock spreads faster for higher reservoir temperature and higher permeability, but it is not sensitive to injection temperature.