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The suns influence on climate is, of course, extremely long-term. In historical times it has had far greater influence on the weather. The mediæval warm period was a weather event, probably caused by climatic and solar cycles coming together in a rare conjunction. It is not precisely understood.
There are several possibilities as to why ice ages come and go. The cooling effects are reasonably well understood. Random events come together to create an unusually long cool period. This removes CO2 and other gases from the atmosphere (primarily CO2), and the greenhouse effect is reduced. Floating ice sheets penetrate the lower latitudes, and they reflect sunlight. The result is a positive feedback cooling loop.
Emergence from an ice age comes from random warming events releasing CO2 to increase greenhouse warming. There are several possible causes, and probably all have played their part in the past, but the most probable is volcanic activity. This has two effects: it releases vast amounts of CO2, and if it occurs at high latitudes melts the ice and deposits large amounts of dark coloured ash onto reflective surfaces.
Mods: Do you agree that we should try not to allow this thread to degrade into a MMGW debate by the back door, as I suspect may have been intended? All questions relating to solar activity and their relevance to MMGW were answered, courteously and in some detail, in the recently-defunct thread, which is still open to readers. |
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