Meteorology and Civilization II

1. Meteorology and Civilization II November 14. 2007

3. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

16. 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

17. Weak, Moderate & Strong La Nina Impacts on Winter Precipitation

18. Weak, Moderate & Strong La Nina Impacts on Spring Precipitation