Meteorology and Civilization II November

Mesopotamia Westerlies brought precipitation from the Mediterranean Precipitation was high enough to support dry-land farming Marginal area Drier hotter lands to the south were irrigated Laborers paid in food

Tell Leilan Akkadian city Abandoned abruptly around 2200 BC Summer rain-bearing winds replaced by hot, dry winds from the north Precipitation dropped by 30% Strong winds blew away topsoil Crops failed, infant mortality increased Citizens moved south where irrigation infrastructure in place, or became pastoral nomads

2200 BC Indus Valley in decline Nile River decreased flow – end of Old Kingdom Amazon suffered the worst drought in 17,000 years Drought recorded in Ireland, Great Plains Caused by volcano? Cooling North Atlantic cuts precipitation in Middle East in half Century-long drought

Dust Bowl If centuries long drought occurred today, implications? Dust Bowl lasted 6 years 3.5 million people relocated Impacted 5 million square miles Thousands of people and livestock died of starvation and respiratory ailments

536 AD Proxy data indicates cooling in western and northern Europe, China, and Korea and drought in Peru, East Africa, India, China, and Korea Not caused by climate cycle Caused by volcano or comet Plague increased when populations of gerbils, mice, and rats increased in Africa

536 AD Collapse of Bantu people in Congo Basin Bantu spent hundreds of years clearing the forest – poor soils The climate change of 536 dried the remaining forest Rapid desiccation of vegetation Agriculture may have allowed plague to enter the Congo

Plague When climate changes, animals must adapt The ones that adapt the fastest are those with the shortest generations and most offspring –Microbes, cockroaches, rats, weeds If climate changes produce more food, populations expand rapidly If climate change produces less food, masses of offspring and short generations allows rapid adaptation

Plague Recent winners in global warming include R-strategists –bark beetles Warmer winters allow them to produce 2 generations a year They also move farther north and higher altitudes Spread to species that have no history of dealing with them

Plague Mosquitoes moving to higher latitudes and altitudes Bringing yellow fever and dengue fever to new populations Hantavirus spread when El Nino-related floods increased the food supply of deer mice and drove them inside

Maya Survived 1200 years in area with little topsoil, little water, and hurricanes Cities built far removed from water sources When one civilization falls, another usually replaces it on the same spot – not so in this case Proxy data points to drought Maya elite used reservoirs to maintain power

Georgia Drought Expected to expand into southeastern Georgia by next summer Water reserves will be depleted by Spring 2008 Implications? –Soil microbes –Fires –erosion La Nina expected in strengthen drought

Weak, Moderate & Strong La Nina Impacts on Winter Precipitation

Weak, Moderate & Strong La Nina Impacts on Spring Precipitation