Climate

Question 1

Controls on climate?

Answer 1

• Changes in the Atmosphere (Composition, circulation)
• Changes in Solar Inputs
• Changes in the Hydrological Cycle
• Biosphere
• Changes in the Cryosphere (Snow, frozen ground, sea ice, ice sheets, glaciers)
• Changes in the land surface (Orography, land use, vegetation, ecosystems)
• Changes in the ocean (Circulation, sea level, biogeochemistry)

Question 2

Importance of Solar Radiation on heating of Earth?

Answer 2

• The Sun is the principle source of energy for the Earth: 3.8x1026 W (J/S)
• Solar constant (for the Earth): S= 1360 W/m2
• Total amount of energy falling on the Earth: S x πR2 = 180000 TW
• Some energy reflected back (albedo): α = 0.3
• Total energy absorbed by Earth: Ein= S(1-α)πR2 = 126000TW
• Ein per square meter of the Earth’s surface: Ein/4πR2 = S(1-α)/4 = 238 W/m2
• From blackbody radiation: P/a = σT4
• T=-18 degrees C

Question 3

What are sunspots?

Answer 3

• Roughly every 11 years
• 400 years of observations
• Only result in irradiance change of about 0.07%
• More sunspots = more solar output

Question 4

Importance of Greenhouse gases?

Answer 4

• EO = σT4 = 30 degrees C
• Atmosphere balances the solar inputs and Earth Surface outputs
• Importance of atmospheric gases
Mercury vs Venus

Question 5

Carbon Cycle?

Answer 5

Carbon cycle:
CO2(g) ⇋ CO2(aq) (Equation 1)
CO2(aq) + H2O ⇋ H2CO3(aq) (Equation 2)
H2CO3(aq) ⇋ HCO3-(aq) + H+(aq) (Equation 3)
CO32-(aq) + H+(aq) ⇋ HCO3-(aq) (Equation 4)
CO32-(aq) + Ca2+(aq) ⇋ CaCO3(s) (Equation 5)

Question 6

Atmosphere – lithosphere exchange

Answer 6

• Equilibrium
• Volcanic eruptions: Release CO2
• Chemical weathering: Takes in CO2 and produces calcium carbonate and SiO2

Question 7

Major CO2 changes:

Answer 7

• Stramatolites - 3.7 Billion Years ago
• First forest - Devonian - 419 Myr - Devonian forests = first source of coal
• Coal swamp
• Himalayan Orogeny - 40-50 Myr
• Ice age
• Industrial revolution - 1857

Question 8

CO2 Record?

Answer 8

• Mauana Loa
• Oldest and most reliable data
• Largest instrumental CO2 record
• Not contaminated by pollution
• Seasonality controlled by northern hemisphere
• On a year-to-year basis, more CO2 released than sequestered

Question 9

What is forcing?

Answer 9

• Radiative Forcing: Change in the Ein-Eout balance before the temperature of Earth has adjusted in response
• RF = Δ(Ein-Eout) = ΔEin - ΔEout
• Positive radiative forcings lead to warmer climate, negative forcing lead to cooler climate

Question 10

Definition of Feedback and examples?

Answer 10

• Is the process in which changing one quantity changes a second quantity, and the change quantity, and the change in the second quantity in turn changes the first

Positive feebacks
• CO2 sorption in warmer oceans
• Permafrost melting – clathrates
• Water-vapour feedback

1. Warming
2. Ice melts
3. Albedo increases
4. More solar energy absorbed
5. More warming
6. Ice melts

Negative feedbacks:

•	Lapse-rate feedback
•	Clouds
•	Primary productivity
•	Chemical weathering
o	More co2
o	More acid
o	More dissolving of silicates

Question 11

Climate Change effects?

Answer 11

•	Not just ‘Global Warming’
•	Rainfall changes are also abundant
•	Drier Mediterranean
•	More humid northern latitudes 
Lake Chad – disappeared by 2001 – was one of the largest lakes in Africa – shifting rain patterns

Question 12

Other climatic changes?

Answer 12

900-1400 - Medieval Warm Period

1450-1550 - Mini Ice Age - 1 degree colder globally