One thing that scientists and conservative Christians may agree on is that there was a garden of Eden six thousand years ago; however, they may not agree on it's location nor its size. The garden I speak of is what is now the Sahara Desert. Ray Pierrehumbert describes the mid-holocene climatic optimum as a time in which forests extended farther north in Europe and rivers flowed in the Sahara (Principles of Planetary Climate, Chapter 1). The wet Sahara was probably a climate response to Earth's orbital precession, Earth's wobbling top-like motion that determines how the sun's energy is distributed globally.
Six thousand years ago seems to have been the warmest and wettest period of the interglacial era that began twelve thousand years ago when the last Ice Age ended. I would like to ask two questions. First, if the increase of carbon dioxide in the atmosphere is allowed to continue, shall we arrive at a climate similar to the climate of six thousand years ago when the Sahara was wet? Second, if we could choose between the climate of today with a dry Sahara and the climate of six thousand years ago with a wet Sahara, should we prefer the climate of today? My second heresy answers yes to the first question and no to the second. It says that the warm climate of six thousand years ago with the wet Sahara is to be preferred, and that increasing carbon dioxide in the atmosphere may help to bring it back. I am not saying that this heresy is true. I am only saying that it will not do us any harm to think about it. (Dyson 2007, Heretical Thoughts about Science and Society)The statements in this passage struck me as odd. I've perused many Holocene climate reconstructions and I didn't recall any prominent global spikes in temperature from this period, but my knowledge is incomplete. As a check on my memory, I consulted some graphs of ice core data plotted for Greenland and Antarctica and confirmed that nothing exceptional affected Greenland and Antarctica: