There have been vast climatic change throughout history. Despite the current frenzy about "global warming", it has all happened before! The ancient world was much colder than today. Archaeology has shown that the sea levels were some 20-30 feet lower than today. The entire middle east was covered by dense forests with abundant rain. this continued through the Roman period. North Africa was the fertile fields where most of the grain was grown for the Roman Empire. From 600-800 there was a period of Earth upheavel resulting in a 200 year period of ice age, plague and famine.