The role of dynamically induced variability in the recent warming trend slowdown over the Northern Hemisphere

Abstract:

In this study, we investigate the recent warming stoppage that started from about 2000 by using a recently developed methodology that can successfully identify and separate the dynamically induced and radiatively forced surface air temperature (SAT) changes from raw SAT data. The results illustrated that the dynamically induced SAT changes exhibited an obvious cooling effect relative to the warming effect of the adjusted SAT in the temperature hiatus process. A correlation analysis suggests that the cooling effect of dynamically induced is dominated primarily by the North Atlantic Oscillation (NAO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). It confirms that dynamically induced variability caused the warming trend slowdown (WTS). The radiatively forced SAT changes are determined mainly by anthropogenic forcing, indicating the warming influence of greenhouse gases (GHGs), which reached levels of 400 ppm during the hiatus period. Therefore, the global SAT will not remain permanently neutral. The increased radiatively forced SAT will be amplified by increased dynamically induced SAT when the natural mode returns to a warming phase in the next period.