Why? What you have shown me is several civilizations that may have ended in part at least because of drought. So a change in climate that results in drought is bad. Is that more likely from warming or cooling? Do you seriously think that the Mediterranean area, the Middle East, or North Africa would be more prosperous if they were hotter?

As this is a discussion thread I will put forward my view for discussion.

When it comes to the effects of CO2 on climate I am not a “Luke Warmer” I subscribe to the view held by Prof. Lindzen “ he responded during the interview with calm, collected answers. His funding comes from the US government. The reason he won't change his mind is that years of scientific research have lead him to the conclusion that the human impact on climate change is negligible.”
Let us take am empirical example. Presumably the CO2 concentrations in the atmosphere are the same over tropical deserts and rain forests on the same latitude. (I have personal experience of both). You will notice that at night the temperature plummets in the desert where as in the rain forest the temperature range is much smaller. This is undoubtedly due to the presence of water vapour because it is assumed that the CO2 concentrations in the atmosphere are about the same. (in fact as the trees absorb CO2 during the day the concentration of CO2 is probably lower). So the impact of water vapour is orders of magnitude greater than that of CO2.

The current IPCC theory depends on the so called positive feedback which has never been demonstrated to exist. Prof. Roy Spencer did a study on water vapour feedback and concluded that if there was any feedback it was slightly negative. ( http://www.drroyspencer.com/2014/09/water-vapor-feedback-and-the-global-warming-pause) This makes sense from our/my experience. When you fly over clouds they are predominantly white reflecting sunlight back to space. If you lay in the sun and a cloud passes over head you instantly sense a drop in temperature. If the cloud was absorbing the heat it would disperse so it must be reflected back out to space. So I believe as Dr. Spencer doses, that the effect of increase water vapour is neutral or slightly negative.

When it comes to sensitivity to doubling of CO2 it is completely meaningless. The assumption is that all the observed warming is due to the increased concentration of CO2 in the atmosphere but there is no justification for that; many other factors may be involved that are not taken into account. The concentration of sunspots and global temperature has a much better co-relation although a linking mechanism has not been confirmed. There is some very interesting work by Henrik Svensmark (http://wattsupwiththat.com/2014/04/10/more-support-for-svensmarks-cosmic-ray-modulation-of-earths-climate-hypothesis/) and Jasper Kirkby. https://www.youtube.com/watch?v=sDo7saKaEys (the lite version) The scientist version (https://www.youtube.com/watch?v=63AbaX1dE7I) The telling graph is 45min onward. He was cautioned by the director of CERN to only report his results and NOT to draw any conclusions. This very important graph was relegated to the appendix in the final paper. Real science at work.
Enjoy the Holocene.

Sorry folks I posted this on the wrong thread.