Dangerous Clarity?

A study by climate change modellers from South Australia (http://www.scientificamerican.com/article.cfm?id=fewer-clouds-could-mean-greater-global-warming ) suggests that failures to consider reductions in cloud cover that would normally reflect a percentage of solar energy the Earth receives back into space have resulted in a marked underestimation of the likely rate of global warming. Their models predict that, rather than the increase, by 2100, being limited to a dangerous but containable 2 degrees Centigrade, the average rise will be a catastrophic 4 degrees. That's the kind of clarity that makes me nervous.