1.7 - Changes To Carbon Cycle (Past, Present, Future)

Question 1

What evidence is there for human induced climate change?

Answer 1

• Natural climate change occurs due to changes in Milankovitch + sunspot cycles, El Niño and ocean oscillations
  
  • however, the change in global temperatures is too great to be explained by natural changes to CO₂ emissions

Question 2

What affect has human activity had on the carbon cycle?

Answer 2

• Carbon has been moved around the cycle, such that it is mostly in the atmosphere
  
  • only half of that CO₂ has been removed by the biological (fast) cycle
• Deforestation reduces the rate of photosynthesis
  
  • thus reducing the speed of the slow cycle
  • limits how much carbon the slow cycle can remove

Question 3

What are the observed affects of the changes made to the carbon cycle?

Answer 3

• carbon particulate concentration has increased
  
  • 310 ppm to 400ppm (1950 - 2016)
  • overall 30% increase
• more carbon has been released from stores
  
  • Fossil Fuels - 375PgC
  • Deforestation - 180PgC
    
    • mostly absorbed by atmosphere (240PgC)
    • This carbon could stay in atmosphere for 2000 years

Question 4

What does the level of CO₂ in the atmosphere dictate?

Answer 4

• CO₂ causes about 20% of climate forcing
  
  • water vapour causes about 50%
• CO₂ provides initial greenhouse heating for water vapour formation
  
  • drop in CO₂ results in Earth cooling, condensation of water vapour
  • thus dictating the amount of water vapour in atmosphere and greenhouse effect

Question 5

What affect does water vapour have in the atmosphere?

Answer 5

• water molecules absorb infrared
  
  • results in radiation that would have been reflected being trapped within atmosphere, creating positive feedback loop
• water in general is a potent GHG, just doesn’t stay in atmosphere for too long due to condensation in normal conditions
• has an overall larger contribution to GHE than CO₂

Question 6

What affect does carbon change have on ecosystems?

Answer 6

• warmer oceans decrease phytoplankton activity (after a certain temp is exceeded)
  
  • limiting fast oceanic carbon sequestration
• increase in CO₂ results in increased phytoplankton growth
  
  • only to a limit as water and nitrogen availability limits growth
• CO₂ increases temperatures, resulting in longer growing season + higher humidity
  
  • however high temperatures can stress plants due to high amount of activity over larger periods of time
• dry plants can easily start forest fires, which release carbon from soil + plants into atmosphere

Question 7

What affect does carbon change have on hydrological systems?

Answer 7

• warmer temperatures leads to more evaporation
  
  • higher humidity + water vapour formation
  • when cooled, falls back as precipitation
• Plant stomata size increases (open up more), resulting in more water loss while more CO₂ is taken in
  
  • water loss decreases rate of growth of new cells, increasing stomata size
  • positive feedback cycle
• drought + heat reduces evapotranspiration, increasing air + surface temps, makes air drier