Longwave Feedbacks in Climate Models
Huang, Y. 2013. On the longwave climate feedbacks. Journal of Climate 26: 7603-7610..
As the Canadian researcher goes on to demonstrate in the body of his paper, "neglecting these two issues may cause a bias in the longwave cloud feedback diagnosed as a residual term in the decomposition of OLR variations." And he notes, in this regard, that his results "and the recent results of others [e.g., the estimate of Zelinka et al. (2012) based on cloud property histograms] indicate that there is, in fact, no consensus in terms of the sign of the longwave cloud feedback among the GCMs." Such sad state of affairs -- that of no consensus, not even in terms of the sign of the longwave cloud feedback -- will likely persist for some time to come, as Huang writes that in order achieve progress, "more studies are still required to understand how clouds modify global warming, even with regard to the longwave aspect alone."
Zelinka, M.D., Klein, S.A. and Hartmann, D.L. 2012. Computing and partitioning cloud feedbacks using cloud property histograms. Part I.: Cloud radiative kernels. Journal of Climate 25: 3715-3735.