Sea-ice formation sustained the 'Little Ice Age'

[ScienceRocks]

Sea-ice formation sustained the 'Little Ice Age'

Volcanic eruptions and reduced solar radiation caused global cooling between the thirteenth and the fifteenth centuries. The resulting accelerated formation of sea ice in the Northern Seas triggered a positive feedback process that shaped the Little Ice Age, as a new study by climate scientists from the University of Bern and the Oeschger Centre for Climate Change Research reveals.

The winter weather in Europe is largely governed by the so-called North Atlantic Oscillation (NAO). This air pressure seesaw between the Azores High and the Icelandic Low produces mild winters in Central and Northern Europe if the two air pressure centres are particularly pronounced and cold winters if they are weak. Until now, the NAO was believed to be jointly responsible for the cooling in the early fifteenth century along with volcanic eruptions and weakened solar radiation. The subsequent Little Ice Age continued into the nineteenth century. Now, however, Bernese climate researchers Flavio Lehner, Andreas Born, Christoph Raible and Thomas Stocker reveal that the Little Ice Age was also able to take its course without the influence of the NAO, driven purely by the consequences of strong and frequent volcanic eruptions at the time, a reduced solar radiation, or both together.

Read more at: Sea-ice formation sustained the 'Little Ice Age'

 

[mamooth]

It's theorized that declining CO2 levels also helped cool the climate.

Bubonic Plague in the old world:

BBC NEWS | Science/Nature | Europe's chill linked to disease
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"Between AD 1200 to 1300, we see a decrease in stomata and a sharp rise in atmospheric carbon dioxide, due to deforestation we think," says Dr van Hoof, whose findings are published in the journal Palaeogeography, Palaeoclimatology, Palaeoecology.

But after AD 1350, the team found the pattern reversed, suggesting that atmospheric carbon dioxide fell, perhaps due to reforestation following the plague.
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And old world diseases reaching the new world:

Columbus' arrival linked to carbon dioxide drop | Humans | Science News
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About 500 years ago, this charcoal accumulation plummeted as the people themselves disappeared. Smallpox, diphtheria and other diseases from Europe ultimately wiped out as much as 90 percent of the indigenous population.

Trees returned, reforesting an area at least the size of California, Nevle estimated. This new growth could have soaked up between 2 billion and 17 billion metric tons of carbon dioxide from the air.

Ice cores from Antarctica contain air bubbles that show a drop in carbon dioxide around this time. These bubbles suggest that levels of the greenhouse gas decreased by 6 to 10 parts per million between 1525 and the early 1600s.
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