·         Mid-6th Century climatic catastrophe, most important date in history of climates' last 2000 years.

·         Mode of research that scientists have been using to look at the history of the Earth’s climate is the study of tree rings.

·         A wide tree ring indicates favorable growing conditions, narrower tree rings indicate poorer growing conditions.

·         By feeding the measurements into a computer database; each ring sequence could be matched with fallen trees and precisely dated.

·         Scientists have found that backing through long ring records of living trees and then overlapping to ring patterns from historic findings: fitting together this information of long ring patterns dating back hundreds to thousands of years.

·         Through this they found that the rings corresponding to the 6th century were abnormally narrow; especially in the oaks.

·         There was an abrupt drop in 536, a little recovery in 537 and 538, and then drops dramatically in 542.

·         These unusual growth patterns imply extreme cold conditions.

·         Climate conditions were missed summers and long stretches of extreme cold.

·         Bad conditions were 536-540’s; implication from many bits of evidence is that.

1)      extremely cold

2)      reduced sunlight

3)      crop failure



Explanations for Extreme Global Cooling & Visible Darkening



·         Dense veil of dust, ash or acid, thrown up into the atmosphere blocking the suns' radiation.

·         Only three types of events could cause something this big: volcano, asteroid, comet

·         For an asteroid to cause a major climatic catastrophe, it would have to have a diameter of 4km across.

·         A comet would have to be 6km because it is less dense than an asteroid and made from gas and ice.

·         If this were the case, there would be evidence of crater 10km large.  There is no evidence of a crater this large on the Earths surface that large.

·         If it hit the ocean there would be historical records of such an occurrence, and there is not.

·         An improved theory is that a fragmented comet scattered through out the atmosphere.

·         The most popular theory is that of a cataclysmic volcano eruption; to support this they studied the historical climates through the polar ice caps.

·         If it was caused by a comet the ice core would contains iridium, if a volcano it would contain sulphates.

·         They found only levels of sulphates, from sulphuric acid in the atmosphere from volcanic eruptions.

·         Through extensive research, they found that the likely cause the major climatic event was caused by the world’s most notorious volcano, Krakatoa.

·         The amount of energy generated by this eruption would have been 2 billion Hiroshima sized nuclear bombs.



Theory of the Effect of Krakatoa on the Climate


·         There would have been towering clouds steam and gas, ash shooting upwards until the point where it would block out the sun in all directions, then move across the sky laterally.  This would be like a natural nuclear winter.

·         Temperatures would drop.  Climate would not have full strength of the sun to evaporate the ocean surfaces, causing less moisture released into the atmosphere.

·         This then would lead to progressively less rainfall, resulting in droughts, famines, and common to the ending of droughts; massive floods.

·         The 6th century had the coldest year of the first millennium, and was the driest period in the last 2000 years.






Krakatoa Island, Indonesia


Krakatoa, the volcano believed to have caused the period known as the Dark Ages.