9.5 pt 1 - Global Climate Change

Question 1

Historic Climate Change

Answer 1

Earth’s climate has varied over geologic time, largely due to variations in earth’s orbit around the sun
- Varies in obliquity (~40,000 yrs.) exposing northern latitudes to higher insolation at different times
- Varies in eccentricity (~100,000 yrs.) bringing it closer to and further from the sun at different times
- More eccentric = further from sun

Leads to predictable variation in Earth’s climate called Milankovitch Cycles

Question 2

Earth’s historical climate

Answer 2

Scientists have measured and estimated earth’s historical temperature and CO2 levels using 3 main pieces of evidence
1. Foraminifera shells in ocean sediments - different species have diff. temp. tolerance
2. Air bubbles in ice cores that contain ancient atmospheric gas (CO2 levels)
3. 16O vs. 18O isotope concentrations in ancient ice ( ⬆️ 18O = ⬆️ temp.)

• Global ice ages, followed by warmer periods occur roughly every 100,000 years
• CO2 levels are strongly correlated with temperature, but causality isn’t fully understood

Question 3

Effects of Climate Change

Answer 3

• Rising Temperature - habitat/species loss, drought, soil desiccation, heat waves, increased precipitation in some regions
• Rising Sea Level - due to glacial, polar ice melt + thermal expansion
• Melting of Permafrost - permanently frozen tundra soils that begin to thaw & release methane & CO2 from anaerobic decomposition

Question 4

Impact on Coastal Communities

Answer 4

• Property loss, damage, potential relocation: Coastal communities, especially poorer ones that can’t build up may need to relocate inland
  - Seawalls or other barriers can be built higher, but this just delays eventual flooding
• Loss of barrier islands: islands that buffer coastal communities/ecosystems from wind & waves may be lost as sea level rises

Question 5

Impact on Atmospheric Currents

Answer 5

• Widening & weakening of hadley cell: as temp. diff. between equator and poles decreases, air ascending and expanding from equator travels further before sinking
  - This shifts subtropical zones (dry, desert biomes) toward the poles and expands the tropics
  - Regions between 300 and 60o may experience drier climate as cool, dry, descending air from hadley cell shifts north & south
• Weakened, destabilized Jet Stream: as arctic warms faster than other areas of earth, temp. difference between equator & poles weakens
  - Because temperature & pressure diff. between polar & subtropical regions is what drives the polar jet stream, less diff. between them means weaker, wobblier jet stream
  • Leads to extreme cold spells in eastern US & dry spells in western US