Attribution of the East Asian Winter Temperature Trends During 1979–2018: Role of External Forcing and Internal Variability.

Attributing the surface air temperature (SAT) trends at regional scale to internally generated and externally forced components is a major challenge. Based on the observations and ensemble simulations of climate models, we apply a "dynamical adjustment" methodology to estimate quantitatively the contribution of the internal and forced dynamic and thermodynamic components to the East Asian winter SAT trends during 1979–2018. The observed winter SAT trends are strongly influenced by internal variability, especially in the northern East Asia (NEA). The internal component of observed SAT trends is largely dynamically induced, whereas the forced component is controlled by thermodynamics. The internally generated variability offsets the forced warming by more than 70% in the NEA, leading to a weak observed warming in the NEA. In contrast, internal contributions are small in the southern East Asia. The internally generated SAT changes in the NEA are closely tied to the multidecadal changes of Arctic Oscillation. Key Points: The observed winter SAT trends are strongly influenced by internal variability, especially in the northern East Asia (NEA)The internally generated variability offsets the forced warming by more than 70% in the NEA, leading to a weak observed warming in the NEAThe internally generated SAT changes in the NEA are closely tied to the multidecadal changes of Arctic Oscillation [ABSTRACT FROM AUTHOR]