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- All models show a negative bias in downwelling surface longwave that tends to get gets systematically worse for warmer and moister atmospheres. No such trend exists for OLR, although there is still a negative bias of typically 0.3 W m-2 that could be improved.
- The radiative forcing by methane tends to be too linear, not capturing the extent of the logarithmic dependence. This is believed to be because the automated procedure for allocating k terms allocates too few to the methane bands, far fewer than are allocated to carbon dioxide, for which the logarithmic dependence is well captured. This could be improved by reducing the error threshold for the allocation of methane k terms.
- ecCKD optimizes both broadband fluxes/heating rates, as well as those in individual bands. As a result, there is some compensation of errors between various bands which is larger than it should be in models with large numbers of k terms.
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