A greenhouse is a very simple thing. What's absurd is to forget to mention than a 3 degrees average rise means a six degrees rise over landmasses. At the deepest of the last glaciation with oceans 120 meters down and ice covering half of Europe and all of Canada, we only had an average of 5 degrees colder than 1900. Holocaust 2.0, your descendants are all invited. (It's Greek for everything burning)