As Dr. Roy Spencer points out in his book,
"The most obvious way for warming to be caused naturally is for small, natural fluctuations in the circulation patterns of the atmosphere and ocean to result in a 1% or 2% decrease in global cloud cover. Clouds are the Earth’s sunshade, and if cloud cover changes for any reason, you have global warming — or global cooling."
This new paper is one of many that demonstrate current climate models do not even approach the level of accuracy [within 1 - 2%] or 'consensus' required to properly model global cloud cover, and therefore cannot be used as 'proof' of anthropogenic global warming, nor relied upon for future projections.
Prior posts on clouds and the abject failure of climate models
Journal of Climate 2012 ; e-View
Simulating clouds with global climate models: A comparison of CMIP5 results with CMIP3 and satellite data
Axel Lauer1,* and Kevin Hamilton1,2
Comparisons of the results from the coupled CMIP5 models with their atmosphere-only versions run with observed SSTs show remarkably similar biases in the simulated cloud climatologies. This suggests the treatments of subgrid-scale cloud and boundary layer processes are directly implicated in the poor performance of current GCMs [global climate models or general circulation models] in simulating realistic cloud fields.