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Middle Miocene Climatic Optimum

1 April 2023
Climate change, Geology

At https://phys.org/news/2023-03-ancient-forests-seaways-climate-lessons.html … this is an article that is supposed to be a climate lesson for us in the 2st century – aka terrifying global warming. It is interesting how much modelling was involved in the research by the Chinese Academy of Sciences – subsequently published in the journal Palaeogeography, Palaeoclimatology, and Palaeoecology [see https://doi.org/10.1016/j.palaeo.2023.111509 ] … which I am supposing is not as alarmist as PhysOrg have as its focus – although no doubt, it would have invovled the obligatory reference in order to be published in a Western journal. The period in question is 16.9 to 14.7 million years ago and is thought to have been characterised by extensive forest coverage. The researchers simulated oceanic circulation using a coupled model called the Flexible Global Ocean-Atmosphere-Land System Model Grid Point Version 3 [FGOALS-g3]. Some proxy data in the suggested co2 concentrations were as high as projected around AD2100. The co2 level in the simulation was assumed to be  similar to that of today – so less co2 to account for the warming. The results indicate the global average temperature was more than 3 degrees higher than the present. Land temperatures were particularly high in what is now the Sahara desert – as well as in northern latitudes. It  does not say which northern regions, but the assumption is that iit involved all the northern zone. Forests are known from some northern latitudes – but is it projection to think all the north was forested?

In addition, there was the open Panama link between the Atlantic and the Pacific, as well as the Tethys Seaway in  what is now Europe, Africa and Asia [or dividing these continental blocks and presumably overlapping some of them]. In other words, it involved a short cut for the Atlantic Meridional Overturning Circulation, a factor in the modern world that is assumed to have been a factor back then.  Lots and lots of assumptions – and a complete absence of the elephant in the room. Most of this can be explained by a modest shift at the poles. Was the Tethys Sea a long term reality as it is based mostly on geochronology and the dating of sedimentary geology. It could have been a more temporary situation with a connection to earth’s geoid – a redistribution of oceanic water as a result of pole movement. The research, in spite of this criticism, is useful as it does show Miocene temperatures differed from those of today. Was the Sahara warmer as it was in a tropical zone at the time, we may wonder.

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