<p>Tibetan Plateau (TP) has been experienced an accelerated surface air warming during recent decades which greatly alters the local hydrological cycle, cryosphere, and ecosystem. The TP warming exhibits a prominent seasonality, but the processes determining the seasonality remain unclear. This study investigates the processes through analyzing air temperature change budget and surface energy balance. The TP warming is relatively weak in summer and spring, but strong in autumn and winter. In summer and autumn, the warming is mainly caused by outside forcing. Anomalous summertime reduction of precipitation over the western North Pacific triggers a circum-global wavetrain that increases heat transport into TP. In autumn, superposition of a zonally-oriented and a meridionally-oriented wavetrains enhances heat transport into TP. The strongest TP warming occurred in winter which is caused jointly by outside forcing and local feedback. The outside forcing originates from the atmospheric warming over the Barents and Kara Seas which triggers a meridionally-oriented wavetrain which increases heat transport into TP. There are two local land-air feedback processes that cause the land surface warming which heats the air aloft via increasing upward sensible heat flux. First, reduced snow cover increases surface-absorbed solar radiation, leading to a snow-albedo feedback. Second, the surface warming tends to strengthen evaporation and moisten the atmosphere aloft, which increases downward longwave radiation and causes a further surface warming, forming a local moisture process feedback. In spring, the outside forcing has a negligible impact on the TP warming, while the warming is mainly caused by increased upward sensible heat flux due to the surface warming which is caused by increased surface absorption of radiation fluxes due to the two local feedback processes.</p>