Earth System Impacts on Humans

Question 1

Earth system impacts on human societies

Answer 1

• 8200 BP event
• The ‘browning’ of the Sahara
• Medieval warm period
• Little Ice Age

Question 2

The 8200 BP event

Answer 2

The Lake Agassiz megaflood 8200 BP caused sea levels to rise 1.4 m -enough to displace
European coastal communities?
Kick-starting European agriculture?

Question 3

The browning of the Sahara

Answer 3

A small change in Earth’s orbit

• leads to a small change in the distribution of solar radiation
• nudges the Earth System across a threshold
• As vegetation reduces the microclimate in the soil changes
• Leads to less vegetation and even drier conditions
• Amplification of initial climate signal caused by positive feedback

Question 4

Medieval Warm Period

AD 950-1250

Answer 4

Evidence for impacts not so easy to find in Europe
Expansion of vineyards northwards in Europe
In Europe few records of famines etc - benign
times?

Question 5

Little Ice Age in Europe

Answer 5

• Cooling 1150-1460 very cold 1560-1850
• Impacted all aspects of life
• Growing season perhaps 15-20% reduced
• Poor grain and wine harvests - 1816 the year ‘without
summer’
• Bad harvest in France 1788 led to bread riots, ‘let them
eat cake’, and the French Revolution?
• Malnutrition - influenza, malaria (ague), bubonic plague
• Abandonment of uplands
• Greater severity of storms
• Widespread Northern hemisphere phenomenon