About the Little Ice Age
You might know about the London fog but back then there was a lot more of it because it was much colder during the little Ice Age.
They say it was less than 1 degrees C colder but that was measured in the summer. They compared the growth of tree rings to find out how much colder it was.
It's true that it was not that much colder in the summer. Sometimes it was only 1 degree C like they say. However, the winters were about 4 degrees colder than now. The reason you don't know this is because tree rings don't grow at all during the winter. Only in the summers.
It wasn't usually a general cooling as caused by volcanic eruptions. It was inclement weather. The summers were strange. Some years both spring and summer would be normal but then fall would start three weeks early and winter likewise. Sometimes we would have two falls. One in August and one in October. It would sometimes go right back to normal for September. At other times during the winter it would drop another 10 degrees C below the already colder temperature. This might happen as late as March. During those times letters from Greece would say their weather had been normal. Sailors that went out during those times said that they met with twice the number of squalls and freak winds. I don't know what was going on. Does anybody?
The summer weather was so subject to these mid summer temperature drops that it literally affected the way we grew out flower gardens. If you want to you can read about it here.
(Thermometers had not been invented yet so weather observations were relative to 'normal weather' and freezing. My quotes of temperatures are only an estimate.)We demonstrate that carefully selected tree-ring chronologies from 14 sites in the Northern Hemisphere (NH) extratropics can preserve such coherent large-scale, multicentennial temperature trends if proper methods of analysis are used.Here
They used a lot of big words but it still doesn't make the tree rings grow in the winter time even one little bit.
When there are reports that the Thames River froze solid they look at that years tree rings and say 'They must be lying since it was not that much colder than it is now'. Well, it wasn't in the middle of the tree growing season when the Thames froze solid.
The first recorded frost fair didn't happen until 1608, but the Thames had frozen over several times in the 16th century. Henry VIII is said to have travelled all the way from central London to Greenwich by sleigh along the river during the winter of 1536 and Elizabeth I took walks on the ice during the winter of 1564. Wikipedia
I don't know if they have a way to determine the winter temperatures like they do the summer temperatures. They should figure out a way. Maybe I can. The sap of some plants change their viscosity in cold weather. Maybe old lumber can be used to see changes in the ratios of the saps produced.
That mini ice age may have been caused by something as simple as ice blocking the current between two islands in the Arctic such as between Greenland and Ellesmere Island where the current is pretty choked off even without ice blocking it. That would have prevented Atlantic water from flowing into the Arctic and that would have caused the Atlantic conveyor belt to move south in the winter. It moves anyway, it would just have moved a lot more then and the Arctic temperature would have tended to move further south in the winters.
With that channel blocked the climate of England and Southern Greenland would partially swap. The conveyor belt would also automatically move farther west since it is dependent in part on the Arctic water coming from between Greenland and Ellesmere to push it eastward towards England. Of course some of the water that came through that gap from the Arctic would then be forced to come south between Iceland and Norway. That would make England a lot colder. That flow would also tend to push the conveyor belt further south and to the west. That would cool off England and Europe even more. This would have had a maximal effect in England but less and less the farther away from there you got. This would have very little effect in America and of course on American tree rings.
Yes there was a general cooling worldwide, even in the southern hemisphere. These were milder changes in the weather than what took place in Europe. Mainly in and around the North Atlantic.
The effect of volcanic erruptions were much more global than what went on across Europe during the Mini Ice Age so I am not even including them.
This map I found here seems to confirm that something similar to this did happened. Look at it from the other direction, those 'arctic water limits' are also the limits of the Atlantic current going northward and the point at which it drops into the deep. It's the northern limit of the warm water of the Atlantic conveyor belt.
Notice how the warm water now goes all the way into the Arctic before it drops. That cooresponds to the present limit of the Arctic water on the first map. However, the first map shows that back in the little Ice Age Arctic water came right down to just north of Scotland which means that the warm water of the conveyer belt dropped west of England and Ireland instead of north of Norway like it does now. Seasonal fluctuations may have moved that critical drop zone point 200 or more miles south during the winters. That would have put the middle of England right at the edge of the arctic during winters. Though the summers would still be warm due to the Atlantic conveyor belt the winters would approach arctic temperatures, just like they often did.
This also explains the large number of squalls and storms at sea. Where there is a confluence of warm and cold water there is also the confluence of warm and cold air. That creates squalls and stormy weather.
This is something I have thought about off and on about since I remembered a few years ago that the winters were much colder than they are now while the summers were often not that much different. Ever since I have been trying to figure out what the mechanism was.
I have not been able to come up with any other scenario that would cause such a wide swing in the temperature between summers and winters.
Maybe it was a lowering of sunspot activity as has been proposed. The only problem is that can't explain the swings between summers and winters or the wild fluctuations in the weather.
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