Global climate models’ bias in surface temperature trends and variability

The Earth has warmed in the last century with the most rapid warming occurring near the surface in the Arctic. This Arctic amplification occurs partly because the extra heat is trapped in a thin layer of air near the surface due to the persistent stable-stratification found in this region. The amount of warming depends upon the extent of turbulent mixing in the atmosphere, which is described by the depth of the atmospheric boundary layer (ABL). Global climate models (GCMs) tend to over-estimate the depth of stably-stratified ABLs, and here we show that GCM biases in the ABL depth are strongly correlated with biases in the surface temperature variability. This highlights the need for a better description of the stably-stratified ABL in GCMs in order to constrain the current uncertainty in climate variability and projections of climate change in the surface layer.