Equilibrium, Feedbacks and Thresholds

Question 1

Negative feedback

Answer 1

system adjusts to lessen or cancel out the effect of initial disruption that has interfered with systems normal operations, equilibrium or balance is restored

Question 2

Positive feedback

Answer 2

Knock on effects that accelerate or amplify any changes that already occur after disruption. Equilibrium upset, system ‘out of control’

Question 3

Carbon positive feedback process

Answer 3

1. global temp rises
2. oceans warm and sea temperatures rise
3. warm water less able to dissolve gas
4. dissolved CO2 is released by oceans and returned back into atmosphere
5. more CO2 as greenhouse gas
6. temperatures rise

Question 4

System threshold

Answer 4

= critical limit that must not be crossed if accelerated and potentially irreversible changes are to be avoided, making it less easy for previous equilibrium state to be restored

Question 5

Cryosphere negative feedback

Answer 5

• loss of ice cover accelerates rise in temp, ice has a high albedo (reflects solar rad), water warms due to darker colour absorbing radiation, ice therefore melts
  1. ice melts, darker ocean exposed, absorbs more sunlight
  2. water warms, level of evaporation increases
  3. more cloud created, reflecting radiation due to high albedo
  4. light absorbed by ocean surface
  5, water temp fall, air mass in contact with it falls

Question 6

Methane feedback

Answer 6

• volumes stored in frozen soils of Earth’s permafrost regions, forming during glacial periods through to holocene (last 10,000 years)
• permafrost melting magnified by +ve feedback:
  1. atmosphere warms, permafrost melt
  2. methane released, (double amount in atmosphere now)
  3. atmosphere warm up more quickly
  4. more methane released through more melting

Question 7

Terrestrial and Marine carbon feedback

Answer 7

• accelerate further as global temp rises
• increase in water vapour in atmosphere, further temp rise, clouds condense and reflect solar radiation
• melting of terrestrial permafrost, methane released
• decrease in ability for sea to absorb co2 as it warms, released rather than absorbed
• ocean acidification impact coral negatively to reduce biological CO2 sequestration in oceans
• rising GMST may change global biome pattern, tree line moves north, coniferous biome grows in size, more C stored

Question 8

Implications of system feedback for life on earth

Answer 8

• high level of uncertainty due to complexity of feedback loops
• potential disappearance of cryosphere
• sustainability threatened by lack of water security for SE Asian region (China home to 1.3bn, 8 megacities)
• summer meltwater feeds rivers, mainly form Himalayan plateau, snowfall replenishes glaciers, over time sustainable
• climate change reducing global ice stores, long term water shortages

Question 9

A ‘wicked’ problem

Answer 9

= challenge that cannot be dealt with easily due to complexity/scale

• uncertainty over feedback loops
• cannot predict economic, demographic, technological and political changes that may influence mitigation efforts