Conclusions
1) The Holocene is a period of 11,700 years characterized by an intense warming for about 2,000 years and a progressively accelerating cooling for the last 6,000 years, following the changes in obliquity of the Earth’s axis.
2) Fluctuations in greenhouse gases cannot explain Holocene climatic changes and, indeed, their concentration changes run opposite to temperature trends for most of the Holocene.
3) Climate models perform very poorly when trying to reproduce Holocene climate evolution. This is likely due to having too much sensitivity to changes in greenhouse gases and too little sensitivity to insolation and solar variability.
4) The Holocene Climatic Optimum was a more humid period, 1-2°C warmer than the Little Ice Age, during which global glaciers reached their minimum extent.
5) The Mid-Holocene Transition, caused by orbital changes, brought a complete change in climatic mode, with a decrease in solar forcing and an increase in oceanic forcing, displacing the climatic equator and ending the African Humid Period, while increasing ENSO activity.
by Javier Vinos
First in a two part series on Holocene climate variability.
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