To understand the individual influences of the land cover, sea temperature, sea ice and carbon dioxide concentration on the global climate, sensitive experiments using the General Atmospheric Circulation Model 4.0 are designed to compare with the observation in this study. Firstly, through the analysis of Liang-Kleeman information flow method, it is straightforward that the pronounced causal relationships exist from these forcing to air temperature. In numerical experiments, the temperature is influenced by the albedo and atmospheric dynamic process. More detailed, in winter, the changes of each forcing will cause the positive Pacific-North American Pattern (PNA) phase, which makes the North American colder. The negative North Atlantic Oscillation (NAO) phase caused by the changes of CO 2 and sea ice induces cold winter over the Europe. This coincides with the extreme cold weather in Europe and North America in 2018. Whereas in summer, all forcings cause positive Arctic Oscillation (AO) phase, resulting in the most northern hemisphere warmer. It is noteworthy that for precipitation, the changes of each forcing increase winds from the sea surface to the land in East Asia, so the precipitable water increases, thus the precipitation overall increases. However, when CO 2 changes, the precipitation decreases due to the lack of dynamic conditions in some areas.

 Both the Arctic and Antarctic ice covers have trans-equatorial climate effects, which can affect the air temperature in the other hemisphere. The interannual variation of Antarctic ice cover even has a greater impact on the surface air temperature over East Asia and North America than the Arctic ice cover. The variance of Antarctic ice cover is closer to the atmospheric midlatitude westerly jet, whose interannual changes could cause more generation of significant atmospheric baroclinic waves and trans-equatorial propagation, resulting in the obvious land surface temperature changes over the Asia and North America.

Using Climate Forecast System Reanalysis (CFSR) data and numerical simulations, the impacts of the multi‐scale sea surface temperature (SST) anomalies in the North Pacific on the boreal winter atmospheric circulations are investigated. The basin‐scale SST anomaly as the Pacific Decadal Oscillation (PDO) pattern, a narrow meridional band of frontal‐scale smoothed SST anomaly in the subtropical front zone (STFZ) and the spatial dispersed eddy‐scale SST anomalies within the STFZ are the three types of forcings. The results of statistical methods find that all three oceanic forcings may correspond to the winter North Pacific jet changing with the similar pattern. Furthermore, several atmospheric general circulation model simulations are used to reveal the differences and detail processes of the three forcings. The basin‐scale cold PDO‐pattern SST anomaly first causes negative turbulent heat flux anomalies, atmospheric cooling, and wind deceleration in the lower atmosphere. Subsequently, the cooling temperature with an amplified southern lower temperature gradient and baroclinity brings a lagging middle warming because of the enhanced atmospheric eddy heat transport. The poleward and upward development of baroclinic fluctuations eventually causes the acceleration of the upper jet. The smoothed frontal‐ and eddy‐scales SST anomalies in the STFZ cause comparable anomalous jet as the basin‐scale by changing the upward baroclinic energy and Eliassen‐Palm fluxes. The forcing effects of multi‐scales SST anomalies coexist simultaneously in the mid‐latitude North Pacific, which can cause similar anomalous upper atmospheric circulations. This is probably why it is tricky to define the certain oceanic forcing to the specific observed atmospheric circulation variation.