In the early stage of processor design, Dynamic Thermal Management (DTM) schemes should be evaluated to avoid excessively high temperature, while minimizing performance overhead as small as possible. In this paper, we show that conventional thermal simulations using fixed ambient temperature may lead to wrong conclusion in terms of performance and temperature; though ambient temperature converges to a steady state after hundreds of seconds, the steady state ambient temperature is significantly different depending on applications. To overcome the inaccuracy of conventional thermal simulations, we propose that architectural thermal simulation should exploit application-dependent ambient temperature. Our evaluation results show that the performance of the same DTM scheme is different, when application-dependent ambient temperature(compared to fixed temperature) is used. For accurate simulation, future architectural thermal researchers are expected to evaluate their proposed DTM schemes, reflecting application-dependent ambient temperature.