Im sorry to be blunt but this just doesnt fly Ruddimans hypothesis is neither here nor there with regard to the cause of recent warming If anything its logically inconsistent to argue that a small change in GHG in preindustrial time did affect climate and yet a large change in GHG in the present day isnt affecting climate And snowball earth was   MYa which is way outside any relevant time frame for current global warming the continents were in completely different places for a start  Finally Ruddiman himself would likely take exception to being thrown in with the scientists objecting camp  the fact that his latest book is Plows Plagues and Petroleum How Humans Took Control of Climate gives a hint as to his stance on recent warming