Week 13

Question 1

Record of temperature from the antarctic ice sheet

Answer 1

• Changes in sea level are not the only thing we learn about climate change from geological proxies. Ice cores also provide valuable information
• Variations in the ratio of lighter and heavier isotopes of oxygen and hydrogen record changes in temperature when the snow fell
• Four complete temperature cycles in the past 450,000 years. Consistent with the ice volume record from the oceans, but much more detailed
• One basic observation is that the past ten thousand years is by no means normal. In fact, it appers to be the longest stable time of the past 400,000 years

Question 2

Other proxy

Answer 2

• glacier length can be related to temperature through some basic physics = glacier length is a proxy for temperature
• measurements of change in the chemistry of tree rings and sediments in the Northern Hemisphere

Question 3

Impact to the human civilization of the Thames river freezes

Answer 3

• Great fluctuation in grain prices during the LIA
• These fluctuations during the little ice age were caused primarily by crop failures associated with more highly variable weather than during previous centuries
• Crop failures led to significant economic problems that in turn led to social and political unrest

Question 4

One very useful proxy for rainfall is in cave deposits

Answer 4

• Mineral laden rainwater drips onto the cave floor and then the water evaporates, Calcite (CaCO3) is the mineral left behind. It forms stalagmites that rises from the floor of the cave
• How do earth scientists date these stalagmites
  1. radioactive uranium in the stalagmite

Question 5

Droughts impact to human civilization

Answer 5

• Changes in dynasty
• What is the lesson for us?
  1. variations in climate can be dangerous to societies and civilizations
• What are the challenges for us?
  1. Political stability
  2. Food Security
  3. Water security
  4. Human Progress

Question 6

Climate change impact at relatively short time scale

Answer 6

• Atmospheric - Ocean Connections in the Pacific ocean
• Walker Circulation Cell: normal conditions
  1. Air pressure across equatorial pacific is higher in eastern pacific
  2. Strong southeast trade winds
  3. Pacific warm pool on western side of ocean
  4. Thermocline deeper on western side
  5. Upwelling off the coast of Peru

Question 7

El-Nino- Southern Oscillation

Answer 7

• Walker Cell circulation disrupted
  1. high pressure in eastern pacific weakens
  2. Weaker trade winds
  3. Warm pool migrates eastward
  4. Thermocline deeper in eastern pacific
  5. Downwelling
  6. Lower Biological productivity: Peruvian fishing suffers

Question 8

Enso impacts

Answer 8

• Occurs around the world
  1. Droughts (e.g Australia, Africa, Brazil, Indonesia)
  2. Floods (e.g Peru, southern USA)

Question 9

La Nina - ENSO Cool Phase

Answer 9

• Increased pressure difference across equatorial pacific
• Stronger trade winds
• Stronger upwelling in eastern pacific
• Shallower thermocline
• Cooler than normal seawater
• Higher biological productivity

Question 10

Occurrence of ENSO events

Answer 10

• El Nino warm phase about 2-10 years
• Higher irregular
• Phases usually last 12-18 months
• 10,000 year sediment record of events
• ENSO may be part of Pacific Decadal Oscillation
  1. Long term natural climate cycle
  2. Lasts 20 -30 years

Question 11

Mitigation: Greenhouse gases

Answer 11

• Need to reduce sources of greenhouse gases
  1. Consume power more efficiently
  2. Act quickly
  3. Change perspective from reacting to short-term threats to recognising the long-term threat
• Simplest, most effective strategies:
  1. Lower transportation-related energy use
  2. Use less fuel to heat or cool homes and buildings
  3. Use energy efficient light bulbs, appliances and insulation
  4. Use alternative energy sources, e.g solar, wind
  5. Minimise deforestations and soil degradation
• Need to amplify sinks for greenhouse gases
  1. Carbon sequestration: artificial
  2. Plants (especially forests) store most of the world’s carbon in leaves, branches, stems and roots: Remains in the plant until it decays or is burned

Question 12

Case study: US!

Answer 12

• Record of atmospheric CO2 for 800,000 years from air bubbles in Greenland and Antarctic ice
• Natural cyclic variation from -200 ppm CO2 to -300 ppm
• 2015 CO2 levels are greater than 400 ppm
• IPPC conclusion: human influence is the dominating cause