Model Biases in the Atmosphere‐Ocean Partitioning of Poleward Heat Transport Are Persistent Across Three CMIP Generations

The observed partitioning of poleward heat transport between atmospheric and oceanic heat transports (AHT and OHT) is compared to that in coupled climate models. Model ensemble mean poleward OHT is biased low in both hemispheres, with the largest biases in the Southern Hemisphere extratropics. Poleward AHT is biased high in the Northern Hemisphere, especially in the vicinity of the peak AHT near 40°N. The significant model biases are persistent across three model generations (CMIP3, CMIP5, CMIP6) and are insensitive to the satellite radiation and atmospheric reanalyzes products used to derive observational estimates of AHT and OHT. Model biases in heat transport partitioning are consistent with biases in the spatial structure of energy input to the ocean and atmosphere. Specifically, larger than observed model evaporation in the tropics adds excess energy to the atmosphere that drives enhanced poleward AHT at the expense of weaker OHT. The equator‐to‐pole contrast of solar radiation entering the climate system drives the large‐scale oceanic and atmospheric circulations that, in turn, move heat from the equator to the poles to moderate latitudinal temperature contrasts. The ocean moves the majority of heat in the tropics whereas the atmosphere moves the vast majority of heat in the mid‐ and polar‐latitudes. We demonstrate that, on average, state‐of‐the‐art climate models representing both oceanic and atmospheric circulations simulate too little oceanic heat transport and too much atmospheric heat transport relative to observational estimates. These model biases in the atmosphere‐ocean partitioning of poleward heat transport are persistent across three generations of climate model ensembles spanning 20 years of progress in climate modeling and are insensitive to the choice of datasets used to calculate observed heat transports. The model biases are consistent with stronger than observed surface evaporation in the tropics which enhances atmospheric heat transport at the expense of oceanic heat transport. Climate models simulate too little poleward oceanic heat transport and too much poleward atmospheric heat transport in the extratropicsModel biases in heat transport partitioning are persistent across model generation and are insensitive to the observational data sets usedStronger than observed evaporation in models enhances atmospheric heat transport at the expense of oceanic heat transport Climate models simulate too little poleward oceanic heat transport and too much poleward atmospheric heat transport in the extratropics Model biases in heat transport partitioning are persistent across model generation and are insensitive to the observational data sets used Stronger than observed evaporation in models enhances atmospheric heat transport at the expense of oceanic heat transport