Pervasive Warming Bias in Climate Computer Games ... er ... I mean the latest CMIP6 climate computer models

Source:

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020EA001281

 

Pervasive Warming Bias in CMIP6 Tropospheric Layers

R. McKitrick

J. Christy

  

"Introduction:

... In previous studies, although a warm bias was typically present, over large atmospheric regions the model spread at least partly overlapped the observational analogs, especially at the global level. 

 

This is no longer the case. 

 

Every model overpredicts warming in both the LT (lower troposphere) and MT (middle troposphere)  layers, in the tropics, and globally. 

 

On average the discrepancies are statistically very significant, and the majority of individual model discrepancies are statistically significant as well."

 

 

"Conclusion: 

The literature drawing attention to an upward bias in climate model warming responses in the tropical troposphere extends back at least 15 years now

 (Karl et al., 2006). 

 

Rather than being resolved, the problem has become worse, since now every member of the CMIP6 generation of climate models exhibits an upward bias in the entire global troposphere as well as in the tropics. 

The models with lower ECS ( climate sensitivity to CO2 ) values have warming rates somewhat closer to observed but are still significantly biased upward and do not overlap observations. 

Models with higher ECS values also have higher tropospheric warming rates, and applying the emergent constraint concept implies that an ensemble of models with warming rates consistent with observations would likely have to have ECS values at or below the bottom of the CMIP6 range.

Our findings mirror recent evidence from inspection of CMIP6 ECSs (Voosen, 2019) and paleoclimate simulations (Zhu et al., 2020), which also reveal a systematic warm bias in the latest generation of climate models."