Often weather is so rigorously bad that it is noticed by trees all over the world and certain dates seem to glare back at us with their unusual distinctions, the dates are 3195 BC, 1628 BC, 2354 BC, 1159 BC, 207 BC, 44 BC and 540 AD.

There is no consensus on why these dates recorded from trees were so dismally bad for trees; either it was volcanic activity or the Earth being hit by a comet or meteor that caused the weather to change overnight.

540 AD the last of these dates is of interest because it had world changing repercussions we live with today.

The historical record:

The Praetorian Prefect Magnus Aurelius Cassiodorus Senator wrote a letter documenting the conditions. "All of us are observing, as it were, a blue coloured sun; we marvel at bodies which cast no mid-day shadow, and at that strength of intense heat reaching extreme and dull tepidity ... So we have had a winter without storms, spring without mildness, summer without heat ... The seasons have changed by failing to change; and what used to be achieved by mingled rains cannot be gained from dryness only."

Another historian, Procopius of Caesarea, a Byzantine, wrote, "And it came about during this year that a most dread portent took place. For the sun gave forth its light without brightness, like the moon, during the whole year, and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear nor such as it is accustomed to shed."

John of Ephesus, a cleric and a historian, wrote, "The sun was dark and its darkness lasted for eighteen months; each day it shone for about four hours; and still this light was only a feeble shadow ... the fruits did not ripen and the wine tasted like sour grapes."

Something happen that changed the weather drastically with world changing repercussions.

In the wake of the inexplicable darkness a monster breeds, the bubonic plague. The plague originated in East Africa, where it existed in fleas which lived on the plague-resistant gerbil. When drought (caused by a dust-laden atmosphere) killed off the larger predators, the gerbil was free to expand its range, spreading its plague-infested fleas to the multimammate mouse, who gave them to the ratlike Arvicanthus, who gave them to Rattus rattus, a worldly, sophisticated rodent who visited all of the popular ports of call, carrying the plague fleas with it.

Its wake would kill one-third of the Roman Empire, four-fifths of Constantinople and its tendrils would even reach China and Britain.

John of Ephesus documented the plague's progress in AD 541-542 in Constantinople, where city officials gave up trying to count the dead after two hundred thirty thousand: "The city stank with corpses as there were neither litters nor diggers, and corpses were heaped up in the streets ..."

In The British Isles the Anglo-Saxons who remained isolated from trade did not suffer as much from the plague as the structure in place, which still had trade ties to Rome. Thus the Anglo-Saxons became the ascendant dominate structure in Britain

On the steppes in Asia another political upheaval was caused by this abrupt weather change- drought. The Avars with their horse-based economy floundered and their vassals the cattle- breeding Turks threw them out. The Avars loaded up their tents and then looked for greener pastures. They eventually settled in Hungary and in cahoots with the Slavs begin to chip away at the Roman Empire.

And in Yemen, in the 540s, a dam broke. By 550 AD, the great Marib Dam, an engineering marvel of the ancient world, was a complete loss and thousands of people migrated to another oasis on the Arabian Peninsula- Medina. The Arab tribes, weakened by famine, begin to rouse themselves and think of conquest. In 610 AD, a new leader unified them--Muhammad.