Historic anthropogenic climate change

1. Historic anthropogenic climate change • We deploy history in several ways in this unit • We review examples of how humans have changed climate in the past • We discuss when the Anthropocene may have began • We review the history of anthropogenic climate change science and policy

2. The Anthropocene • Marks era when humans begin to modify Earth on a pervasive global basis • When it began is debated. These proposed events below are associated with pronounced changes in carbon budgets and climate • When humans modification of the Earth’s surface expanded globally during the Neolithic Revolution. • European contact and depopulation and reforestation of the Americas • During the Industrial Revolution when fossil fuels began to be used on a large scale • During the Great Acceleration, the emergence and growth of a global economy after World War

3. Neolithic Revolution (10,000 years ago) • Deforestation and conversion to agriculture • Domestication of plants and animals • Accompanied by human population expansion • Impact on carbon budgets and climate

4. Cahokia Mounds (southern Illinois) Contact between Europe and the Americas • Prior to European arrival, North and South American landscapes had been highly modified by large numbers of native Americans. • Grasslands kept open thru the use of fire • Earthworks, roads, fields common, large expanses of forests cleared • Agricultural clearing over large areas Large relict agricultural fields in S. America

7. Pre-contact Americas may have held as many people as in Europe at that time • Estimates range up to 50-90 million • After arrival of smallpox and influenza (flu), population greatly reduced population The Olmec, Aztec, Maya, Inca, Toltec – all had large cities and these are the regions in which their cultures flourished until European colonization.

8. The Orbis Spike • A sharp drop in carbon dioxide and a period of cooling temperatures around 1610 that marks European contact with the Americas

9. The Industrial Revolution (1780 to 1945) • Began with burning of coal for steam power in Europe • However, coal was being used in China 800 years earlier • Coal gave way to consumption of oil derived from drilling into rocks

13. The Great Acceleration • Began in the 1950’s • Marked global economic expansion following the end of World War 2 • Advances in technology and medicine catalyzed by war effort played role

15. How has the way in which humans have viewed their place in the world changed? Darwin (1859) Copernicus (1543)

16. The place of human during the Anthropocene • Our awareness of global human impacts on climate and ecosystems is unprecedented • Humans now recognize their ability to shape the evolution of the Earth by their actions • Power humans wield is unique because it is reflexive: it can be used, withdrawn or modified.

17. Nuclear winter (1980s)