I think you'll find modern research has concluded that the past climatic phenomena you mention, ( often thrown on the table by man-induced global warming sceptics trying to prove that the current climate change is due to natural causes) were in fact regional & not global. Or if you prefer, their effects were only felt by a part of the earth & not globally.Please read the links i put up, the medieval warm period was global. The little ice age was global. The Roman warm period affected Britain, as grapes were first grown here at that time. Solar cycles do not have regional affects.
The Eddy solar cycle (circa 1000 years) correlates to the dates of each. At maximum during the roman period, at min during the dark ages, max at medieval period, min during little ice age, and rising towards its maximum now. 500 years between each peak and trough, 1000 years between each peak.
Roman warm period peaked 100ce, medieval peaked 1100ce, modern period will peak around 2100.
Dark age cold period bottomed out around 600ce, little ice age bottomed out around 1600ce.
If we take the 'Medieval Warm Period" for example, though Europe may have benefited from a milder climate at the time, ice activity around the North Atlantic was only marginally less than during the 'Mini Ice age'...(which of course was not a true ice age)
Additioning the parts of the globe which were much cooler at the time than today, such as the tropical pacific, the global temperature is estimated to be equivalent to that of the mid 20th century & in all likelyhood, temperatures today across the northern hemisphere are warmer now than they were during the M.W.P.
During the 'Roman Warm Period' the warming of the Mediterranean sea did affect the climate throughout a large part of the Roman Empire' & of course grapes were first grown at this period in England, since vines were introduced by the Romans, who also had the wine making knowledge that the Britons didn't have. But it would be misleading to suggest that the UK had a mediterranean climate at the time, when in reality the weather was prehaps no different than a good English summer today. The extreme weather events that now regularly occur in the Mediterranean regions, far exceed anything that those who lived during this Roman period experienced, which was a period of relative climatic stability, always a bonus when creating a civilisation.
But all that is beside the point, other than to illustrate that the climate has changed in the past without man's help, which no one denies, it can't be used as evidence that our current climate woes are not due to human activity . Comparing past climatic changes, ( which all had different causes such as solar activity, variations in the Earth's orbit, inclination of it's axis to changes in ocean currents or the jet stream,) the causes of which cannot account for today's rising global temperature, is like comparing cancer with heart disease. It isn't because the earth was hotter 800 million years ago that the same factors are generating today's global warming.
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