Fig. 2.

Surface albedo trend and attribution. (A) Time evolution of area- and energy-weighted average of annual-mean surface albedo over the Arctic during 1980 to 2014 from CAM5 (red) as well as using a surrogate model (black). The Arctic albedos derived from these 2 methods are highly correlated (R = 0.99, P < 0.01). (B) Contributions to surface albedo trend from SCF change over Arctic land. (C) Same as B but over Arctic ocean. (D) Same as C but for contributions from sea ice fraction change. In all panels, the solid line is a linear least-squares fit, of which the slope represents the trend in units of % decade⁻¹ (marked in each panel). All of the regression coefficients are statistically significant at the 99% confidence level.